Endangered and Threatened Wildlife and Plants; Notice of 12-Month Finding on a Petition To List Bottlenose Dolphins in Fiordland, New Zealand as Threatened or Endangered Under the Endangered Species Act, 35306-35317 [2015-15087]

Agencies

• DEPARTMENT OF COMMERCE
• National Oceanic and Atmospheric Administration

[Federal Register Volume 80, Number 118 (Friday, June 19, 2015)]
[Notices]
[Pages 35306-35317]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2015-15087]


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DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

[Docket No. 150106016-5016-01]
RIN 0648-XD703


Endangered and Threatened Wildlife and Plants; Notice of 12-Month 
Finding on a Petition To List Bottlenose Dolphins in Fiordland, New 
Zealand as Threatened or Endangered Under the Endangered Species Act

AGENCY: National Marine Fisheries Service (NMFS), National Oceanic and 
Atmospheric Administration (NOAA), Commerce.

ACTION: Notice of 12-month petition finding.

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SUMMARY: We, NMFS, announce a 12-month finding on a petition to list 
bottlenose dolphins (Tursiops truncatus) within Fiordland, New Zealand 
as threatened or endangered under the Endangered Species Act (ESA). 
Based on our review of the best scientific and commercial data 
available, we have determined that the bottlenose dolphins within 
Fiordland do not meet the criteria for identification as a distinct 
population segment. Therefore, these dolphins do not warrant listing, 
and we do not propose to list these dolphins under the ESA.

DATES: This finding was made on June 19, 2015.

ADDRESSES: Information used to make this finding is available for 
public inspection by appointment during normal business hours at NMFS, 
Office of Protected Resources, 1315 East West Highway, Silver Spring, 
MD 20910. The petition and the list of the references used in making 
this finding are also available on the NMFS Web site at https://www.nmfs.noaa.gov/pr/species/petition81.htm.

FOR FURTHER INFORMATION CONTACT: Lisa Manning, NMFS, Office of 
Protected Resources (OPR), (301) 427-8403.

SUPPLEMENTARY INFORMATION:

Background

    On July 15, 2013, we received a petition from WildEarth Guardians 
to list 81 marine species as threatened or endangered under the 
Endangered Species Act (ESA). We found that the petitioned actions may 
be warranted for 27 of the 81 species and announced the initiation of 
status reviews for each of the 27 species (78 FR 63941, October 25, 
2013; 78 FR 66675, November 6, 2013; 78 FR 69376, November 19, 2013; 79 
FR 9880, February 21, 2014; and 79 FR 10104, February 24, 2014). Among 
the 27 species that we determined may warrant listing under the ESA is 
the bottlenose dolphin, Tursiops truncatus, of Fiordland, New Zealand. 
This finding addresses those bottlenose dolphins.
    We are responsible for determining whether species are threatened 
or endangered under the ESA (16 U.S.C. 1531 et seq.). To make this 
determination, we consider first whether a group of organisms 
constitutes a ``species'' under the ESA, then whether the status of the 
species qualifies it for listing as either threatened or endangered. 
Section 3 of

[[Page 35307]]

the ESA defines a ``species'' to include ``any subspecies of fish or 
wildlife or plants, and any distinct population segment of any species 
of vertebrate fish or wildlife which interbreeds when mature.'' On 
February 7, 1996, NMFS and the U.S. Fish and Wildlife Service (USFWS; 
together, the Services) adopted a policy describing what constitutes a 
distinct population segment (DPS) of a taxonomic species (the DPS 
Policy, 61 FR 4722). The DPS Policy identifies two elements that must 
be considered when identifying a DPS: (1) The discreteness of the 
population segment in relation to the remainder of the species (or 
subspecies) to which it belongs; and (2) the significance of the 
population segment to the remainder of the species (or subspecies) to 
which it belongs. As stated in the DPS Policy, Congress expressed its 
expectation that the Services would exercise authority with regard to 
DPSs sparingly and only when the biological evidence indicates such 
action is warranted.
    Section 3 of the ESA defines an endangered species as ``any species 
which is in danger of extinction throughout all or a significant 
portion of its range'' and a threatened species as one ``which is 
likely to become an endangered species within the foreseeable future 
throughout all or a significant portion of its range.'' We interpret an 
``endangered species'' to be one that is presently in danger of 
extinction. A ``threatened species,'' on the other hand, is not 
presently in danger of extinction, but is likely to become so in the 
foreseeable future (that is, at a later time). In other words, the 
primary statutory difference between a threatened and endangered 
species is the timing of when a species may be in danger of extinction, 
either presently (endangered) or in the foreseeable future 
(threatened).
    Section 4(a)(1) of the ESA requires us to determine whether any 
species is endangered or threatened due to any one or a combination of 
the following five threat factors: The present or threatened 
destruction, modification, or curtailment of its habitat or range; 
overutilization for commercial, recreational, scientific, or 
educational purposes; disease or predation; the inadequacy of existing 
regulatory mechanisms; or other natural or manmade factors affecting 
its continued existence. We are also required to make listing 
determinations based solely on the best scientific and commercial data 
available, after conducting a review of the species' status and after 
taking into account efforts being made by any state or foreign nation 
to protect the species.

Species Description

Taxonomy and Physical Characteristics

    The common bottlenose dolphin, Tursiops truncatus, is one of the 
most well-known and well-studied species of marine mammals. The 
bottlenose dolphin is a cetacean within suborder Odontoceti (toothed 
whales) and family Delphinidae. Up to 20 separate species have been 
proposed at various times as a consequence of bottlenose dolphins' 
geographically diverse and highly plastic physical characteristics. 
Although uncertainty and debate remain regarding their taxonomic 
status, two species of Tursiops are now generally recognized--the 
common bottlenose, Tursiops truncatus, and the Indo-Pacific bottlenose, 
T. aduncus (Connor et al. 2000). A third species, T. australis, which 
occurs along the southern coast of Australia, has been recently 
proposed (Viaud-Martinez et al. 2008) but is not yet formally accepted. 
The bottlenose dolphins in Fiordland, New Zealand have been placed in 
T. truncatus based on their longer length; smaller beaks, flippers, and 
dorsal fins; and lack of ventral spotting, which is common in T. 
aduncus and very rarely seen on T. truncatus (Wang et al., 2000; 
Boisseau, 2003). This classification has since been supported by 
genetic data (Tezanos-Pinto et al. 2008).
    In general, the bottlenose dolphin body form is described as being 
robust with a short, thick beak. Their coloration ranges from light 
gray to black with lighter coloration on the belly. Coastal animals are 
typically smaller and lighter in color, while pelagic animals tend to 
be larger, and darker in coloration. Dolphins living in warm, shallow 
waters also tend to have smaller body sizes and proportionately larger 
flippers than animals living in cool, deep waters (Hersh and Duffield 
1990; Chong and Schneider 2001).
    Bottlenose adults range in length from about 1.8 to 3.9 m, with 
some even larger sizes reported for some populations from the southern 
hemisphere (Leatherwood et al., 1983). Based on measurements of two 
carcasses and stereophotogrammetry (a technique for obtaining 
measurements from photographs) of live dolphins from one fiord 
(Doubtful Sound), the bottlenose dolphins in Fiordland appear to be 
morphologically similar to pelagic animals and those in temperate 
coastal regions, but larger and more robust in body form than 
bottlenose dolphins in lower latitudes (Chong and Schneider 2001; 
Boisseau 2003). The two carcasses measured were of an adult, 7-year old 
male that was 3.2 m long and a sub-adult 3-year old female that was 2.8 
m long (Boisseau, 2003). Asymptotic total length in adult bottlenose 
dolphins in Doubtful Sound is predicted to reach at least 3.2 m (Chong 
and Schneider 2001). Sexual dimorphism of Fiordland bottlenose dolphins 
may also occur, with males potentially reaching larger sizes than 
females (Boisseau, 2003). Based on laser photogrammetry (also known as 
laser-metrics) on 20 adult females and 14 adult males, Rowe and Dawson 
(2008) found that adult males in Doubtful Sound have significantly 
taller and wider dorsal fins than adult females; however, the 
differences were not such that adults could be sexed in the wild on the 
basis of their dorsal fins.

Range and Distribution

    Bottlenose dolphins are found in tropical and temperate waters 
around the world from roughly 45[deg] N. to 45[deg] S. (Leatherwood and 
Reeves, 1983) but are also known to occur in latitudes greater than 
45[deg] in multiple locations within both hemispheres (e.g., United 
Kingdom, northern Europe, South Africa, New Zealand, and Tierra del 
Fuego; Ross 1979; Jefferson et al. 2008; Olavarria et al. 2010; Goodall 
et al. 2011). The species includes coastal populations that migrate 
into bays, estuaries, and river mouths, as well as offshore populations 
that inhabit pelagic waters along the continental shelf. Movement 
patterns of bottlenose populations vary, with some exhibiting long-term 
residency, seasonal migrations, or even fully pelagic lifestyles. 
Individual ranges can be influenced by water temperature and associated 
prey distributions (Hansen 1990; Wells et al., 1990), and use of 
separate areas to hunt for various preferred prey is not uncommon 
(Defran et al., 1999; Sotckin et al., 2006). Other factors that may 
affect habitat use include predation pressure (Mann et al. 2000; 
Heithaus and Dill 2002) and anthropogenic disturbance (Lusseau 2005b; 
Bejder et al. 2006).
    Bottlenose dolphins have a discontinuous distribution within the 
coastal waters of both the North and South Islands of New Zealand. The 
three main coastal regions where they commonly occur are along the 
northeastern coast of the North Island, Marlborough Sounds, and 
Fiordland (Figure 1).
    Bottlenose dolphins have been reported in many of the fiords within 
Fiordland, and sightings along the west coast down to Stewart Island 
off the southern coast of the South Island are fairly common (Boisseau 
2003). Scientific surveys within Fiordland were first initiated in 1990 
(Boisseau 2003), but have focused on only a few

[[Page 35308]]

of the 14 fiords where bottlenose dolphins are known to occur. The 
Doubtful-Thompson Sound complex (hereafter Doubtful Sound)--the second 
largest and best studied of the fiords--hosts a small, resident 
population of bottlenose dolphins. Bottlenose dolphins also occur in 
the Dusky- Breaksea Sound complex (hereafter Dusky Sound) and Milford 
Sound; however, surveys of these fiords are more limited. Anecdotal 
reports have been made of large groups of bottlenose dolphins in Dagg 
Sound and Preservation Inlet, which lie to the north and south of Dusky 
Sound, respectively (Figure 1; Boisseau 2003); and, between 1996 and 
2009, there were five reports of groups of 5 to over 100 individuals 
(Currey 2008b) in Chalky and Preservation Inlets (Figure 1). Based on 
very limited photo-identification data, these dolphins were presumed to 
be visitors from one or more other populations and not Fiordland 
residents (Currey 2008b). We are not aware of any dedicated survey 
efforts in these fiords where dolphins have been occasionally reported. 
For those fiords that have been surveyed, more detailed information on 
the range and distribution of the dolphins is summarized below.
    The bottlenose dolphins in Doubtful Sound have been described as 
being highly resident: Almost all adults are observed during each 
survey (Henderson et al. 2013), and re-sighting probabilities are 
extremely high (mean = 0.9961, 95% CI: 0.9844-0.9991; Currey et al. 
2009b). However, the range of these dolphins is not fully understood 
and may be changing. A review of historical sightings data indicates 
that during 1994-2003, there were only three instances of five or more 
dolphins leaving the fiord for more than 3 consecutive days (Henderson 
et al. 2013). Boisseau (2003) also reported that on rare occasions, 
single dolphins and mother-calf pairs from this fiord made offshore 
forays and were absent from the fiord for weeks to months. In 2009, a 
group of 15 dolphins that were photo-identified residents of Doubtful 
Sound were photographed in Dagg Sound (Henderson et al. 2013). Since 
then, the number of documented occurrences of dolphins leaving the 
fiord has increased in frequency (Henderson et al. 2013). Between 
November 2009 and October 2011 (with 22-35 total survey days per year), 
there have been six documented occasions of groups of 6 to 47 dolphins 
leaving the fiord for a minimum of 3 to 7 days. It is unlikely that 
dolphins were simply missed during the surveys, because this population 
is small (61, CV = 1.46%), the individuals were photo-identified using 
strict protocols, and survey effort was relatively high (Henderson 
2013a; Henderson et al. 2013). These missing groups included roughly 
equal numbers of males and females and included adults, sub-adults, and 
calves (Henderson et al. 2013). Every individual in this population was 
absent on at least one of these six occasions and on an average of 3.55 
of these occasions (SE = 0.28); but all were observed during later 
surveys (so had not died or permanently emigrated; Henderson et al. 
2013). Causes of this apparent change in residency have not yet been 
determined. Destination of the dolphins once they leave is also 
unknown; however, on two occasions in 2011, Henderson et al. (2013) 
observed large groups moving out of Thompson Sound and heading north, 
and there are reports of Doubtful Sound dolphins to the south in Dagg 
Sound and Dusky Sound (Currey et al., 2008b, citing L. Shaw, pers. 
comm.; Tezanos-Pinto et al. 2010, citing G. Funnell, pers. comm.).
    Surveys of Dusky Sound are more limited. Currey et al. (2008c) 
obtained an asymptotic discovery curve and a high re-sighting rate of 
bottlenose dolphins in this fiord complex during summer 2007/2008, and 
thus concluded the dolphins were resident at least over the limited 
study period. Following the same survey methods as Currey et al., 
(2008c), Henderson (2013a) conducted surveys from February 2009 to 
February 2012 in Dusky Sound (about 34 survey days per year), and after 
the first survey in 2009, did not identify any ``new'' dolphins (other 
than calves), which is further indication of population residency. 
During all of the surveys spanning 2007-2012, groups of 2-5 dolphins 
were missing on four occasions (Henderson 2013a). These ``missing'' 
dolphins were typically older males, and because they were always 
present in later surveys, permanent emigration was ruled out. Dusky 
Sound is relatively large, so it is possible the surveys failed to 
capture these particular dolphins. There are only two documented cases 
where dolphins identified as part of the Doubtful Sound population have 
been observed in Dusky Sound (Currey et al., 2008b, citing pers. comm. 
(Lance Shaw)): In 2003, two older males from Doubtful Sound were 
observed in the presence of other bottlenose dolphins, and one of the 
two (``Quasimodo'') was observed in Dusky Sound again in 2005.
    Within northern Fiordland, bottlenose dolphins have been most 
studied within Milford Sound, where dolphins are present throughout the 
year and where there is a significant amount of boat traffic and 
tourism. The bottlenose dolphins of Milford Sound are part of a more 
transient population that ranges across at least 6 fiords, several 
bays, and a lake system from Lake McKerrow south to Charles Sound 
(Figure 1; (Lusseau 2005a). Some photo-identified individuals have even 
been reported just north of Fiordland in Jackson Bay, which lies about 
60 km north of Lake McKerrow (Russell et al., 2004; as cited in 
Tezanos-Pinto et al., 2010). Given that Milford Sound is relatively 
small (15.7 km long, 1.6 km wide on average; Stanton & Pickard, 1981), 
it is probably not adequate to support a resident population (Lusseau 
and Slooten 2002). Published surveys of the remainder of the known 
range of these dolphins appear to be lacking.
    Seasonal and spatial distribution patterns of bottlenose dolphins 
appear to vary among fiords. In Doubtful Sound, the dolphins show a 
preference for the inner fiords during summer and the outer fiord 
during winter and spring (Elliott et al. 2011; Henderson 2013b). This 
pattern was positively correlated with surface water temperature, and 
dolphins were rarely sighted in water below 8[deg] C (Henderson 2013b). 
It is possible that the dolphins prefer warmer water or that they are 
following seasonal changes in prey distributions. However, it is likely 
that thermal stress on calves, which are born in the summer and autumn, 
explains the dolphins' avoidance of the inner fiords during winter 
months ((Elliott et al. 2011). In all seasons, the dolphins remained 
close to the fiord walls (Henderson 2013b). In contrast, during their 
early and late summer surveys of Dusky Sound, Currey et al. (2008c) 
found that the dolphins occurred throughout the entire fiord system. In 
a separate study, the dolphin distribution within Dusky Sound was 
positively correlated with surface water temperature during winter 
only, and in no season were the dolphins found in close association 
with the fiord walls as in Doubtful Sound (Henderson 2013b). Currey et 
al. (2008c) hypothesize that the differences in seasonal distributions 
for the Doubtful and Dusky sounds, which are only 46 km apart at their 
entrances, are due to oceanographic conditions specific to each fiord.
    Distribution patterns of bottlenose dolphins within the northern 
fiords are not yet well understood and have only been evaluated in 
Milford Sound. Gaskin (1972, as cited in Lusseau, 2005) indicated that 
during ship surveys from 1968-1970, bottlenose dolphins were commonly 
observed in Milford Sound in summer but rarely during winter. Sighting 
network data for 1996-1999 also suggest that bottlenose dolphins are

[[Page 35309]]

less common in this fiord during colder months (Lusseau and Slooten 
2002). However, a more recent study, in which Lusseau (2005b) surveyed 
Milford Sound with equal effort across four seasons, indicated that the 
dolphins occur in the sound more frequently in winter (December-
February). Lusseau (2005b) proposed this change in habitat usage may be 
the result of increased boat traffic in Milford Sound during the summer 
season.
[GRAPHIC] [TIFF OMITTED] TN19JN15.000

Habitat

    Fiordland is a mountainous region extending along more than 200 km 
of the southwest coast of the South Island (Figure 1). It includes 14 
major fiords and their associated arms. The 14 fiords range in length 
from 15 km to 38 km (Gibbs et al. 2000) and can reach depths greater 
than 400 m (Heath 1985). Carved by Pleistocene glaciers (26,000-18,000 
years ago), the 14 major valleys in Fiordland were once freshwater 
lakes; then, about 12,000-6,000 years ago, sea level rose above the 
terminal moraine or sill at the mouths of the valleys, inundating them 
with seawater (Wing and Jack 2014). The underwater sills (30-145 m 
deep) still partially separate the fiords from the Tasman Sea (Heath 
1985). The region receives a tremendous

[[Page 35310]]

amount of orographic precipitation (i.e., relief-associated rainfall)--
up to 6-8 m per year (Gibbs et al. 2000). The large volume of 
freshwater input along with the deep bathymetry, narrow tidal range, 
and somewhat limited ocean swell within the inner fiords, contribute to 
a persistent and precipitous salinity stratification within the fiords 
(Wing and Jack 2014). Greater wave action and mixing, however, occurs 
near the fiord entrances (Wing and Jack 2014). Temperature of the low 
salinity upper layer varies seasonally and typically ranges from 12-17 
[deg]C, but can reach temperatures as low as 4 [deg]C in some areas 
during winter (Heath 1985; Henderson 2013b).
    The fiords support highly endemic and diverse invertebrate and 
microalgae communities (Wing and Jack 2014). The inner fiords are 
characterized by an abundance of sessile invertebrate communities that 
include species of bivalves, tube worms, bryozoans, sponges, 
brachiopods, cnidarians and ascidians (Wing and Jack 2014). Closer to 
the fiord entrances, there is a dramatic transition to macroalgae 
communities and kelp forests (Wing and Jack 2014). The diversity of 
habitats across the depth and length of each fiord support many higher 
tropic level consumers, including deep water species like rattails 
(Caelorinchus spp.) and hagfish (Eptatretus cirrhatus), rocky reef 
species like spotty (Notolabrus celidotus) and conger eel (Conger 
verrauxi), and pelagic fishes like mackerel (Scomber australasicus and 
Trachurus declivis). The most heavily fished species in Fiordland are 
blue cod (Parapercis colias), the red rock lobsters (Jasus edwardsii), 
and sea perch (Helicolenus percoides).
    Fiordland is only sparsely populated by people but does support 
considerable tourism (hiking, scenic cruises, diving, etc.). In 1952, 
New Zealand established the Fiordland National Park, which covers an 
area of 1.26 million hectares. The national park is also recognized as 
a United Nations Educational, Scientific and Cultural Organization 
(UNESCO) World Heritage Site, Te W[amacr]hipounamu. Bordering the 
national park are 10 marine reserves, ranging in size from 93 to 3,672 
hectares. In total, the marine reserves cover more than 10,000 hectares 
of marine habitat within the inner fiords.

Life History and Reproduction

    The bottlenose dolphin lifespan is 40-45 years for males and more 
than 50 years for females (Hohn et al., 1989). Long-term observations 
of identifiable dolphins in Fiordland suggest some may be as old as 40 
years (Boisseau 2003; Reynolds et al. 2004). Age at sexual maturity in 
bottlenose dolphins varies by population and ranges from 5-13 years for 
females and 9-14 years for males (Mead and Potter 1990). In a long-term 
study within Doubtful Sound, Henderson et al. (2014) calculated a mean 
age of 11.33 years (95% CI: 10.83-11.83) at first reproduction for 
three females of known age.
    Single calves are born after a gestation period of about a year, 
but weaning and calving intervals vary among populations. Calves are 
nursed for a year or longer and remain closely associated with their 
mothers. On average, calving occurs every 3 to 6 years, and calves 
remain associated with their mothers for roughly 3-6 years (Read et al. 
1993). The calving interval of bottlenose dolphins in Doubtful Sound 
ranges from 1 to 10 years and is highly dependent upon calf survival 
(Henderson 2013b). For example, Henderson (2013b) found that when 
calves died within a month of birth, their mothers could produce 
another calf the following year; and, for mothers with calves surviving 
for longer than a year, the average inter-calving interval was 5.3 
years.
    In general, bottlenose dolphin length at birth is about 0.9 m to 
1.2 m (Leatherwood et al., 1983). To our knowledge, sizes of calves 
born in Fiordland have not been reported. Based on laser photogrammetry 
measurements of dorsal fin base length, Rowe et al. (2010) found that 
calves in Doubtful Sound (n = 4) were smaller at first measurement than 
calves in Dusky Sound (n = 11), suggesting they were either born later 
in the season or were smaller at birth.
    While calving can occur throughout the year, seasonal peaks in 
calving occur in many populations, especially those in cooler, 
temperate regions (Urian et al. 1996; Henderson et al., 2014). The 
bottlenose dolphins of Doubtful Sound show a strong birthing peak in 
warmer months of the austral summer (Boisseau 2003). In a 16-year study 
(1995-2011), Henderson et al. (2014) documented that calving in 
Doubtful Sound occurs from October-April but mainly takes place during 
December-February, when average water temperatures grow increasingly 
warmer. Calving in Dusky Sound appears to have a less pronounced 
seasonal peak and occurs from early December to May or June (Rowe et 
al. 2010).
    Reproductive life is fairly long in bottlenose dolphins, and 
females as old as 48 years have been known to raise healthy calves 
(Boisseau 2003). Additional, specific life history information for 
bottlenose dolphins within Fiordland is lacking.

Diet and Foraging

    Bottlenose dolphins are generalists and eat a wide variety of 
fishes and invertebrates that reflects both their preferences and the 
availability of prey (Corkeron et al. 1990). They are known to forage 
both individually and cooperatively and use multiple strategies to 
capture prey, such as passive listening, prey herding, and ``fish 
whacking'' using their flukes (Reynolds et al. 2000).
    Stomach content analyses for Fiordland bottlenose dolphins are not 
available. However, a stable isotope analysis comparing isotope ratios 
in exfoliated skin tissue samples from dolphins (n = 11) inside 
Doubtful Sound provides some indirect information on their diet 
(Lusseau and Wing 2006). This analysis suggests that, at least within 
Doubtful Sound, the dolphins' diet consists mainly of reef-associated 
fish (e.g., wrasses, perch, eel) and other demersal fish species (e.g., 
cod, sea perch; Lusseau and Wing 2006). Pelagic fishes, which enter the 
fiord from the adjacent Tasman Sea (e.g., mackerel and squid), and 
other deep basin species (e.g., hagfish and rattails) do not appear to 
comprise much of the dolphins' diet (Lusseau and Wing 2006). These 
results are consistent with observations of dolphins spending the 
majority of their time and diving mostly in areas associated with rocky 
reefs along the fiords' walls or sills in which demersal and reef-
associated fish are most commonly found. In Milford Sound, tour 
operators have reported observing bottlenose dolphins feeding on 
yellow-eyed mullet, flounder, eels and trout (Lusseau and Slooten 
2002).
    For dolphins in Doubtful Sound, some observations suggest 
cooperative feeding through synchronous diving, and tour operators in 
Milford Sound have reported observing bottlenose dolphins cooperatively 
feeding on yellow-eyed mullet by herding and trapping them against the 
wall of the fiord (Lusseau and Slooten 2002). However, individual 
diving and feeding appear to be more common (Boisseau 2003). Passive 
acoustic monitoring of dolphins within Doubtful Sound suggests that the 
dolphins forage more frequently at dawn and especially dusk (Elliott et 
al. 2011).

Mortality

    Natural predators of bottlenose dolphins are mainly shark species, 
including bull, dusky, and tiger sharks (Shane et al. 1986). Bottlenose 
dolphins in Fiordland are observed with scars

[[Page 35311]]

that may be from shark-attacks (Boisseau 2003), but predation rates 
have not been estimated. Anthropogenic sources of mortality appear to 
be limited and may predominately consist of boat strikes, which have 
been the focus of some conservation concerns (Lusseau 2005; Lusseau et 
al. 2006). The mortality rate for the dolphins in Doubtful Sound has 
been estimated at 8% per year, which is similar to rates measured for 
coastal populations in Florida (e.g., 7-9%; Boisseau 2003).

Behaviors

    In general, the daily behaviors of bottlenose dolphins are 
categorized into several activities, such as travelling, socializing, 
foraging, milling, or resting. Activity budgets may depend on seasonal, 
ecological, and other factors (Reynolds et al. 2000). In Doubtful 
Sound, the group behavioral budget has been quantitatively divided into 
travelling, resting, milling, diving, and social behaviors (Boisseau 
2003). About half of the dolphins' behavioral budget is spent on 
travelling, which in this case, is defined as movement in a uniform 
direction with short, regular dive intervals (Boisseau 2003). The 
dolphins' behaviors also appear to vary between the warmer, summer 
months and the colder, winter months. In the warmer summer months, the 
dolphins spend about 12 percent of their time milling and about 22 
percent of their time socializing. (``Milling'' is defined as no net 
movement of the group, with individuals typically surfacing facing 
different directions. ``Socializing'' involves many aerial behaviors, 
physical contact, and the formation of small, tightly spaced clusters.) 
In winter, these activities accounted for only 4 percent (milling) and 
11 percent (socializing) of the budget (Boisseau 2003). Presumably, the 
increase in social behaviors in the summer is associated with mating 
activities. In winter, diving also increases to about 22 percent of the 
budget (versus 16 percent in summer), possibly reflecting higher energy 
requirements in colder months (Boisseau 2003). In Milford Sound, the 
dolphins spend a greater proportion of their overall behavioral budget 
diving compared to the dolphins in Doubtful Sound (32 percent versus 22 
percent; Boisseau, 2003). Socializing (15 percent) and resting (9 
percent) are smaller portions of the overall budget for Milford Sound 
dolphins when compared to those in Doubtful Sound (20 percent and 13 
percent, respectively). Boisseau (2013) hypothesized that the dolphins 
use Milford Sound primarily as a foraging ground.
    In the wild, bottlenose dolphins may occur alone but are often 
observed in groups. Group sizes are highly variable and depend on a 
range of physical and biological factors such as physiography, prey 
availability, and behavioral state (Shane et al. 1982; Reynolds et al. 
2000). In general, group size tends to increase with water depth or 
distance from shore (Shane et al. 1982; Reynolds et al. 2000). Coastal 
groups often contain about 2-15 dolphins, compared to offshore groups, 
which can contain about 25 to over a thousand dolphins (Reynolds et al. 
2000; Scott and Chivers 1990; Leatherwood et al. 1983). Social 
structure within bottlenose dolphin populations is described as being a 
``fission-fusion'' structure in which smaller groups form, but group 
membership is dynamic and can change on a fairly frequent basis (e.g., 
hours to days; Connor et al. 2000). This fission-fusion society 
involves long-term, repeated associations between and among individual 
dolphins rather than constant associations; however, some long-term 
stable associations between individual dolphins are also observed and 
can last for years or decades (Reynolds et al. 2000).
    Based on seven years of systematic surveys in Doubtful Sound (1995-
2001), Lusseau et al., 2003 reported an average group size of 17.2 
dolphins (median = 14, n = 1,292), with a skewed distribution towards 
smaller groups sizes (mode = 8). Most groups were of mixed sex, and the 
social structure appeared to consist of three main groups, each with a 
large proportion of strong and relatively stable relationships (Lusseau 
et al. 2003). In Dusky Sound, a median group size of 11.3 dolphins 
(quartiles: 25% = 6.0, 75% = 19.2; n = 46) was reported by Lusseau and 
Slooten (2002) based on sightings network data from 1996 to 1999. For 
Milford Sound, Lusseau and Slooten (2002) reported that group size 
ranged from less than 5 to more than 40, with a median of 16.4 
(quartiles: 25% = 9.0, 75% = 22.7; n = 508). Group size in Milford 
Sound also varied across the length of the fiord, with larger groups 
more common at the entrance to the fiord, and smaller groups typically 
found within the fiord (X\2\ = 33.71, df = 12, p <0.001; Lusseau and 
Slooten 2002). Understanding of the social structure within the fiords 
to the north and south of Doubtful Sound is lacking (Boisseau 2003).

Abundance and Trends

    Monitoring of the bottlenose dolphins within Doubtful Sound has 
been ongoing since 1990, and using data from standardized surveys 
conducted during 1990-1992, Williams et al. (1993) applied three 
different models to estimate a total population size of about 58 
dolphins. Based on a survey completed in 2007, Currey et al. (2007) 
estimated a total population size of 56 dolphins (1.0% CV); and most 
recently, Henderson (2013a) estimated a population size of 61 dolphins 
(CV = 1.5%) for 2012. Other than calves, no new dolphins have been 
sighted in this fiord since 2004; thus, immigration is probably rare 
(Currey et al. 2007; Henderson 2013a). Based on sightings data from 
2007-2011, adult survival rates are very high (0.988, 95% CI: 0.956-
0.997), and despite an increase since 2010, calf survival rates are 
quite low (0.622, 95% CI: 0.435-0.830; Henderson 2013a). Between 1995 
and 2011, the average birth rate for dolphins in Doubtful Sound was 
4.11 calves per year (SD = 2.49; Henderson 2013b). The majority of runs 
(62%) of an age-structured stochastic population model indicate this 
population is declining (Henderson 2013b).
    Bottlenose dolphin surveys in Dusky Sound were initiated in 2007, 
and based on survey data from 2007-2008, Currey and Rowe (2008) 
estimated a resident population totaling 102 bottlenose dolphins (CV = 
0.9%). More recently, Henderson (2013a) completed a 4-year survey of 
Dusky Sound in 2012 and reported a population census of 124 dolphins, 
which closely matched the match-recapture estimate of 122 dolphins (CV 
= 0.83%). Henderson (2013a) also reported that no new adults or sub-
adults have been identified in this fiord since 2009, suggesting that 
immigration may be rare. Adult survival rates in Dusky Sound are high 
(0.966, 95% CI: 0.944-0.98), but calf survival rates are quite low 
(0.722, 95% CI: 0.556-0.844, Henderson 2013a). The majority of runs 
(60%) of an age-structured stochastic population model indicate a 
negative population trend (Henderson 2013b).
    The bottlenose dolphin abundance within Milford Sound has been 
estimated to be only about 45 to 55 total individuals (Lusseau et al. 
unpubl. data, as cited in Lusseau 2005). Boisseau (2003) also reported 
a provisional abundance estimate of 47 individuals (CV = 6.5%) for 
Milford Sound. It is unclear how fully these estimates account for the 
other 6 fiords that this northern community of dolphins is known to use 
as part of its range. To our knowledge there are no other abundance 
estimates or trend information available for this population.
    Based on the separate abundance estimates for Doubtful, Dusky, and 
Milford Sounds, the total abundance of

[[Page 35312]]

bottlenose dolphins in Fiordland is probably close to 200 dolphins. 
Similarly, based on recent abundance estimates for Doubtful and Dusky 
Sounds and stochastic modeling for Milford Sound, Currey et al. (2009a) 
estimated a total population of 205 bottlenose dolphins in Fiordland 
(CV = 3.5%, 95% CI: 192-219). Using stochastic age-structured Leslie 
matrix population models, Currey et al. (2009a) also projected that the 
Fiordland population was highly likely to decline over the next one, 
three, and five generations.

Distinct Population Segment Analysis

    The following sections provide our analysis of whether the 
petitioned entity--the bottlenose dolphins occurring within the waters 
of Fiordland, New Zealand--qualify as a DPS of Tursiops truncatus. To 
complete this analysis we relied on the best scientific and commercial 
data available, and we considered all literature and public comments 
submitted in response to our 90-day finding (79 FR 9880; February 21, 
2014).

Discreteness

    The Services' joint DPS Policy states that a population segment of 
a vertebrate species may be considered discrete if it satisfies either 
one of the following conditions:
    (1) It is markedly separated from other populations of the same 
taxon as a consequence of physical, physiological, ecological, or 
behavioral factors. Quantitative measures of genetic or morphological 
discontinuity may provide evidence of this separation.
    (2) It is delimited by international governmental boundaries within 
which differences in control of exploitation, management of habitat, 
conservation status, or regulatory mechanisms exist that are 
significant in light of section 4(a)(1)(D) of the ESA (61 FR 4722; 
February 7, 1996).
    For purposes of this analysis, we defined the population segment of 
bottlenose dolphins of Fiordland to consist of the three communities 
that occur regularly in, or originate from, Milford Sound, Doubtful 
Sound and Dusky Sound. We use the term ``community'' here to mean a 
group of dolphins that share a common home range; whereas, we use the 
term ``population'' to apply more strictly to a closed reproductive 
unit. We considered the range of the possible Fiordland DPS to extend 
as far north as Jackson Bay. The more transient community of dolphins 
that occur in Milford Sound may range at least as far north as Jackson 
Bay, which is about 60 km north of Lake McKerrow at the northern edge 
of Fiordland (Figure 1; Russell et al. 2004, as cited in Tezanos-Pinto 
et al. 2010). Groups of bottlenose dolphins ranging in size from 2 to 
over 100 dolphins have been occasionally sighted as far south as 
Preservation Inlet but are of unknown origin (Currey 2008b). Lacking 
any basis to exclude the southernmost fiords, we considered the 
geographic range of the possible Fiordland population segment to extend 
as far south as Preservation Inlet. Dolphins that are only occasional 
visitors and not resident to Fiordland were not considered in our 
analysis as part of the potential distinct population segment.
    There are no physical barriers preventing migration or movement of 
bottlenose dolphins out of Fiordland. Groups of dolphins from both 
Doubtful and Dusky Sound are known to have traveled outside their 
fiords (Henderson 2013a; Henderson et al. 2013), and are thus not 
restricted to a particular fiord. The bottlenose dolphins occurring in 
northern Fiordland are also known to range over at least 7 fiords and 
possibly as far north as Jackson Bay, and they are considered to have a 
home range of at least 250 km (Boisseau 2003). Documented movements of 
other coastal populations of bottlenose dolphins in New Zealand 
indicate that the bottlenose dolphins elsewhere in New Zealand waters 
undertake long migrations. For example, a photo-identified bottlenose 
dolphin was sighted off of Westport only 66 days after having been 
sighted in Marlborough Sounds, indicating it had covered over 370 km in 
a maximum of 66 days (Figure 1; Brager and Schneider 1998). The 
bottlenose dolphins that occur in the Bay of Islands, which lies at the 
northernmost end of the North Island of New Zealand, are also known to 
travel to the Hauraki Gulf, over two hundred kilometers to the south 
(Berghan et al., 2008), and their range, at minimum, extends 82 km 
north and 388 km south of the Bay of Islands (Constantine 2002).
    Despite the long-range movements and lack of physical barriers, the 
closest bottlenose dolphin sightings north of Fiordland come from 
Westport, which is about 400 km north along the coast from Jackson Bay, 
and dolphins are only reported to occur there occasionally (Brager and 
Schneider 1998). Similarly, bottlenose dolphins have only been 
occasionally sighted in the southernmost fiords, to the south of Dusky 
Sound (Figure 1; Boisseau 2003; Henderson 2013a). Thus, there may be 
some degree of geographic separation of the Fiordland population as a 
consequence of existing distribution patterns.
    A range of physiological, ecological, and behavioral factors can 
act as mechanisms to create or maintain separation among populations. 
In this particular case, we examined possible mechanisms, such as 
breeding cycles, diet, foraging strategies, and acoustic repertoires 
that could contribute to the marked separation of the Fiordland 
dolphins. As discussed previously, the breeding and birthing cycles of 
the Fiordland dolphins are seasonal, with births peaking in the warmer 
months. This reproductive cycle, however, is likely to coincide or at 
least overlap with that of other New Zealand populations. For example, 
for the Bay of Islands population in the North Island of New Zealand, 
the majority of calves are born in the summer months (Constantine 
2002). In fact, most global populations exhibit diffuse seasonality, 
with birthing peaks occurring in the warmer months (Urian et al. 1996). 
The varied diet and variety of foraging strategies that have been 
reported for dolphins in Fiordland suggest that these factors are also 
unlikely to create ecological barriers to mixing with other populations 
or communities. The acoustic repertoire of Fiordland dolphins is highly 
diverse and does include some vocalizations that may be unique to 
Fiordland (Boisseau 2005). However, many of the vocalizations are 
similar to those reported elsewhere (Boisseau 2005), and acoustic 
studies on other coastal New Zealand bottlenose dolphin populations 
appear to be lacking, thereby precluding comparisons. Other relevant 
data, such as social organization within and among communities of 
bottlenose dolphins of coastal New Zealand, also appear to be very 
limited and could not provide evidence of marked separation. After 
examining the best available information, we ultimately concluded there 
is insufficient evidence of particular physiological, ecological, or 
behavioral mechanisms contributing to the marked separation of the 
Fiordland dolphins from other bottlenose dolphin populations.
    As highlighted in the DPS Policy, quantitative measures of 
morphological discontinuity or differentiation can serve as evidence of 
marked separation of populations. We examined whether the morphological 
data for bottlenose dolphins in Fiordland, which come from a limited 
number of dolphins from Doubtful Sound, provide evidence of marked 
separation of the Fiordland dolphins. As discussed previously, the 
asymptotic total length for adult bottlenose dolphins in Doubtful Sound

[[Page 35313]]

is predicted to reach at least 3.2 m, which is about 30 percent longer 
than adult bottlenose dolphins from the warmer-water populations in 
Texas and Florida (Perrin, 1984, Chong and Schneider 2001). Based on 
stereophotogrammetric measurements, fluke width and anterior flipper 
length also appear to be proportionately smaller for bottlenose 
dolphins in Doubtful Sound when compared to stranded bottlenose 
dolphins from Texas (Chong and Schneider 2001). The morphology of the 
Doubtful Sound dolphins is consistent with the general pattern of 
increasing body size with decreasing water temperatures and is similar 
to that of other deeper water populations and populations in higher 
latitudes (Ross and Cockcroft 1990; Hersh and Duffield 1990). 
Bottlenose dolphins elsewhere in New Zealand also exhibit longer body 
sizes, and as noted by Constantine (2002), the bottlenose dolphins in 
the Bay of Islands ``appear to be morphologically the same as those in 
Marlborough Sounds and Doubtful Sound.'' In the Bay of Islands, which 
lies along the northeast coast of the North Island, four corpses of 
presumed members of that region's coastal population, had measured 
lengths of 2.84 m, 3.12 m, 3.13 m, and 3.16 m, comparable to the 
estimated length of Fiordland dolphins (Constantine 2002, citing 
unpublished data). Other data, such as skull measurements, which would 
allow for additional morphological comparisons, do not appear to be 
available for the Fiordland dolphins. Overall, we concluded there is no 
evidence of marked separation of the Fiordland population segment on 
the basis of a quantitative morphological discontinuity.
    Photo-identification libraries, in which known individuals are 
catalogued based on dorsal fin markings, have been generated and 
maintained for many of the coastal populations of bottlenose dolphins 
in New Zealand, including Doubtful, Milford and more recently, Dusky 
Sound. These libraries allow tracking of the demographics and 
individual status of dolphins within the dolphin communities. Over 17 
years of photo-identification records have been amassed from surveys of 
Doubtful Sound and provide firm evidence that the dolphins of Doubtful 
Sound are fairly resident and have a high degree of natal philopatry 
(Henderson et al. 2013; Henderson et al. 2014). In surveys conducted 
from 2009-2012 in Dusky Sound, Henderson (2013a) also reported that no 
new adults or sub-adults were identified in the fiord after 2009, 
suggesting that immigration is limited or rare. While movements of 
dolphins outside of their main fiord have been documented, especially 
for Doubtful Sound, no permanent emigration has been reported, and the 
only new individuals identified in each community have been calves 
(Henderson 2013a). The lack of documented emigration or immigration in 
the datasets for both Doubtful and Dusky Sounds is a strong indicator 
that these communities are probably closed, and thus markedly separate 
from other coastal New Zealand or pelagic populations. Although there 
remains some uncertainty given the limited data for the community that 
frequents Milford Sound and for dolphins occurring in the southernmost 
fiords, we consider the survey data for Doubtful and Dusky Sounds, the 
two largest fiord systems in Fiordland, to be evidence of the 
demographic independence of the Fiordland population and thus marked 
separation of the Fiordland population segment from other bottlenose 
dolphin populations.
    The hypothesis that the Fiordland dolphins are demographically 
independent is supported by genetic data that indicate restricted gene 
flow among New Zealand bottlenose dolphin populations. Analyses of 
mitochondrial DNA (mtDNA) control region sequences (n = 193) and 11 
nuclear microsatellite loci (nuDNA, n = 219) indicate that three 
discontinuous, coastal populations of bottlenose dolphins in New 
Zealand--the northeastern North Island, Marlborough Sounds, and 
Fiordland populations--are relatively genetically isolated from each 
other (overall mtDNA Fst = 0.15, p < 0.001; overall nuDNA Fst = 0.09, p 
< 0.001; Tezanos-Pinto et al. 2008; Tezanos-Pinto et al. 2010). All 
pairwise comparisons of the three sample populations based on both 
mtDNA and nuDNA also indicate significant genetic differentiation (p < 
0.001 for all Fst comparisons, Tezanos-Pinto et al. 2010). Within the 
Fiordland sample, which included samples collected from Jackson Bay (n 
= 5) and Doubtful Sound (n = 14), three dolphins shared an mtDNA 
haplotype with the North Island population and one dolphin shared a 
haplotype with the Marlborough Sounds population (Tezanos-Pinto et al. 
2010). The remaining four haplotypes in the Fiordland sample were 
unique to the Fiordland dolphins (Tezanos-Pinto et al. 2010). Tezanos-
Pinto et al. (2010) found no evidence of genetic sub-structuring within 
the combined Fiordland sample (i.e. Jackson Bay and Doubtful Sound); 
however, sample sizes were too small to allow rigorous statistical 
analysis. Tezanos-Pinto et al. (2008) also conducted a global 
assessment of genetic structure within T. truncatus by pooling the 
mtDNA samples for the three New Zealand populations and comparing that 
pooled sample to 13 other regional populations or subpopulations from 
the South Pacific, North Pacific and Atlantic Oceans (n = 579). 
Overall, all sample populations were significantly differentiated (Fst 
= 0.16, [Fcy]st = 0.34, p< 0.0001), and all pair-wise comparisons with 
the New Zealand sample population were also significant (p < 0.0055; 
Tezanos-Pinto et al. 2008); however, there were no phylogeographically 
distinct lineages at a regional scale. Tezanos-Pinto et al. (2010) also 
noted that the relatively large number of mtDNA haplotypes (n = 6) and 
high levels of haplotype and nucleotide diversity for the Doubtful 
Sound sample (h = 0.82  0.056, nucleotide diversity = 1.54 
percent  0.83) are inconsistent with expectations of 
genetic drift in a small isolated population (e.g., < 50 mature 
females). This diversity could reflect relatively recent isolation or 
periodic interbreeding with neighboring communities or pelagic 
populations. We further note there are significant limitations of the 
currently available data due to the lack of genetic samples from the 
pelagic populations off New Zealand and from other communities within 
Fiordland. Thus, there is still considerable uncertainty regarding the 
degree of genetic isolation of the bottlenose dolphins within 
Fiordland, and further research is needed to more fully resolve the 
population structure.
    Although the currently available genetic data do not support a 
conclusion that the Fiordland bottlenose dolphin population segment 
constitutes a completely separate population segment, the available 
genetic data do indicate varying magnitudes of differentiation of New 
Zealand dolphins from other global populations. Considering the 
available genetic data and the evidence of closed populations within 
Fiordland, we conclude that the weight of the evidence is sufficient to 
indicate that the Fiordland bottlenose dolphins are markedly separated 
from other populations of T. truncatus. Thus, after considering the 
best available data and information, we conclude that the Fiordland 
population segment of bottlenose dolphins is ``discrete.'' We therefore 
proceeded to evaluate the best available information with respect to 
the second criterion of the DPS Policy.

[[Page 35314]]

Significance

    Under the DPS Policy, if a population segment is found to be 
discrete, then its biological and ecological significance to the taxon 
to which it belongs is evaluated. This consideration may include, but 
is not limited to: (1) Persistence of the discrete population segment 
in an ecological setting unusual or unique for the taxon; (2) evidence 
that the loss of the discrete population segment would result in a 
significant gap in the range of a taxon; (3) evidence that the discrete 
population segment represents the only surviving natural occurrence of 
a taxon that may be more abundant elsewhere as an introduced population 
outside its historical range; and (4) evidence that the discrete 
population segment differs markedly from other populations of the 
species in its genetic characteristics (61 FR 4722, February 7, 1996). 
Significance of the discrete population segment is not necessarily 
determined by the existence of one of these classes of information 
standing alone. Accordingly, all relevant and available biological and 
ecological information for the discrete population segment is 
considered in evaluating the discrete population segment's importance 
to the taxon as a whole.

Persistence in an Ecological Setting Unusual or Unique for the Taxon

    Bottlenose dolphins occur in a wide range of habitat types around 
the world. Within the range of the species, there is no typical or 
usual habitat type in terms of water depth, proximity to shore, water 
temperature, salinity, or prey resources. Provided there are sufficient 
prey resources, bottlenose dolphins can be successful in very diverse 
habitat conditions. For example, bottlenose dolphins occur in shallow, 
coastal bays, lagoons and estuaries; waters around oceanic islands; and 
in deep, offshore waters. They are found in warm, tropical waters as 
well as colder temperate waters, generally no farther than 45 degrees 
North or South (Leatherwood and Reeves 1983). The waters of Fiordland 
are an example of a colder, deeper water, coastal habitat at the 
southern limit of the species' range. Other and even more extreme 
occurrences of bottlenose dolphins have been recorded in relatively 
cold and/or deep-water habitats in the northern hemisphere, such as in 
Moray Firth, Scotland (57 degrees N; Cheney et al. 2013) and off the 
coast of Norway (Tomilin 1957, as cited in Kenney 1990) and southern 
Greenland (Leatherwood and Reeves 1982), and in the southern 
hemisphere, for example in the Patagonian and Fuegian channels and 
fiords (as far as 53 degrees S; Olavarria et al. 2010; Cheney et al. 
2013). Thus, while Fiordland, New Zealand is a biologically and 
geologically unique region towards the southern limit of the species' 
range, the persistence of bottlenose dolphins in this region is not in 
itself significant to the taxon as a whole.
    The Petitioner asserted that Fiordland bottlenose dolphins have 
developed adaptations in response to their persistence in their cold-
water habitat and that these differences qualify them as 
``significant'' under the DPS Policy. Specifically, the Petitioner 
cites the larger body size as an adaptation stemming from their cold-
water habitat and an indicator of the ``significance'' of the Fiordland 
dolphins. The Petitioner also discusses the dolphins' ``unusual'' 
seasonal distribution patterns, larger group sizes, and distinct social 
structure. Thus, we considered possible adaptations to the particular 
ecological setting and whether they indicate that the bottlenose 
dolphins in Fiordland are ``significant'' to the taxon as a whole.
    As discussed previously, the morphology of the Fiordland bottlenose 
dolphins appears to be consistent with the general pattern of 
increasing body size with decreasing water temperatures, similar to 
that of other deep water populations and populations in higher 
latitudes (Hersh and Duffield 1990; Ross and Cockcroft 1990; 
Constantine 2002). For example, bottlenose dolphins found in Tierra del 
Fuego, South America, reach lengths over three meters, and eastern 
North Atlantic dolphins, like those in Moray Firth, Scotland, measure 
as long as 3.8 m (Perrin and Reilly 1984; Goodall et al. 2011). Even 
larger body lengths of up to 4.1 m have been recorded for bottlenose 
dolphins in the northeastern Atlantic (Connor et al. 2000, citing 
Frazer 1974 and Lockyer 1985). It has been hypothesized that a larger 
body size provides a thermal advantage in colder water by reducing the 
surface-area-to-volume ratio (Ross and Cockcroft 1990). In colder 
waters, the proportionally smaller appendages may also help minimize 
heat loss by decreasing the surface area-to-volume ratio (Boisseau 
2003; Ross and Cockcroft 1990). Likewise, smaller body sizes and 
proportionally larger flippers in warmer waters may in part be a 
consequence of the greater requirement for heat dissipation (Hersh and 
Duffield 1990). This pattern of increased body size and smaller 
appendages is common in both terrestrial and marine species found 
across a wide range of latitudes, and is thus not unique to bottlenose 
dolphins (Boisseau 2003; Reynolds et al. 2000). In summary, the 
Fiordland population's morphological characteristics are neither 
unexpected given its habitat nor unobserved in other bottlenose dolphin 
populations. This information strongly suggests that larger body size 
is not a unique adaptation to Fiordland but is part of the observed 
variability for the taxon; therefore, we conclude this characteristic 
does not qualify this population segment as significant to the taxon as 
a whole.
    In general, group sizes observed for the Fiordland bottlenose 
dolphin communities are considered relatively large. As discussed 
earlier, group sizes vary among the three Fiordland communities, and 
the reported medians from a study of all three communities were 11.3 (n 
= n = 46), 16.4 (n = 508), and 21.2 (n = 568) for Dusky, Milford, and 
Doubtful Sound, respectively (Lusseau and Slooten 2002). In Milford 
Sound, group size also varied significantly depending on location 
within the fiord, with larger groups being more common near the 
entrance to the fiord (Lusseau and Slooten 2002). Based on observations 
of 1,292 groups followed in Doubtful Sound from 1995 to 2001, Lusseau 
et al. (2003), found that group sizes ranged from less than 5 to over 
55 dolphins and averaged 17.2 dolphins (median = 14).
    Although large compared to many coastal, resident populations, the 
reported group sizes for the Fiordland dolphins is not dissimilar from 
group sizes reported for other coastal populations in New Zealand. For 
example, group size for bottlenose dolphins in the Bay of Islands was 
found to range from an average of 18.1 dolphins in Spring (median = 20, 
range = 2-50, n = 31) down to a low of 13.8 in Winter (median = 12, 
range = 2-40, n = 50, Constantine 2002). Dwyer et al. (2013) reported a 
high level of year-round use of the waters off the west coast of Great 
Barrier Island, which lies at the outer edge of Haukari Gulf, North 
Island, by ``large groups'' with a median size of 35 (other statistics 
were not available). Lastly, in the Marlborough Sounds, South Island, 
group size was found to range from 3-172 dolphins, with a median size 
of 12 (n = 45, SD = 38), and with most groups (n = 34) containing more 
than 11 dolphins (Merriman et al. 2009).
    Group size for Fiordland dolphins is also similar to, or even 
smaller than, group sizes reported for bottlenose dolphins occurring in 
the comparably cold and deep water habitats of Patagonia. Based on 32 
separate sightings recorded during 2001-2010 in the Patagonian fiords 
of southern Chile, Olavarria et al. (2010) reported that

[[Page 35315]]

group size ranged from 2-100 and averaged 25 dolphins. Similarly, in 
eight sightings of bottlenose dolphin groups over the course of 14 
surveys during 2000-2001 in the northern Patagonia fiords of southern 
Chile, Viddi et al. (2010) reported group sizes of 4-100 dolphins and 
an average group size of 34. In addition, when compared to other 
bottlenose populations generally, the group sizes reported for 
Fiordland are well within the observed variability. For example, Scott 
and Chivers (1990) reported fairly large mean and median group sizes of 
94 and 12, respectively, for coastal bottlenose dolphins in the eastern 
tropical Pacific Ocean (n = 867); and Zaeschmar et al. (2013) reported 
groups sizes ranging from 2-250 dolphins and averaging 62.8 dolphins in 
waters off the northeastern coast of the North Island, New Zealand (n = 
36, SD = 42.8).
    Group size may be affected by factors such as presence of 
predators, prey availability, habitat complexity, season, and activity 
type (e.g., foraging, breeding; Shane et al. 1986; Heithous and Dill 
2002; Gowans et al. 2008). Whether and how these and other ecological 
factors influence group size has received inconsistent support in the 
literature, complicating researchers' ability to establish general, 
consistent relationships between group size and ecological factors 
(Scott and Chivers 1990; Corkeron 1997; Gygax 2002; Gowans 2008). It 
remains unclear the extent to which variation in group size across the 
species is a result of random historical processes versus selective 
pressures (Gygax 2002). Perhaps lesser but additional complications 
hampering interpretations of group size are the differing perceptions 
of what constitutes a group, and inconsistencies among studies in terms 
of the criteria used to define ``a group'' (Shane et al. 1986; Connor 
et al. 2000).
    Overall, given the natural variability of group size observed in 
bottlenose dolphins, the similarity of group sizes within Fiordland to 
those reported elsewhere, and the lack of a clear understanding of the 
drivers of this variation, we find there is insufficient evidence that 
the group sizes reported for Fiordland communities reflect a special or 
unique adaptation to their habitat such that it qualifies the 
population segment as ``significant'' to the taxon as a whole.
    A characteristic related to group size is social structure, and as 
discussed earlier, bottlenose dolphins are highly social animals 
exhibiting a ``fission-fusion'' social structure (Connor et al. 2000). 
The ``fission-fusion'' social structures of bottlenose dolphins is 
highly plastic and ranges dramatically among communities or populations 
from being characterized by a high proportion of long-lasting 
associations (Lusseau et al. 2003) to consisting mostly of short-term 
(several days) associations (e.g., Lusseau et al. 2006). Complexity of 
the overall social structure also varies widely and can include few or 
many levels of organization and alliances. Influences that contribute 
to inter- and intra-population variation in social structure may 
include availability of prey, disturbance, dispersal, and other 
demographic factors (Ansmann et al. 2012; Augusto et al. 2012; Morteo 
et al. 2014; Hamilton et al. 2014). Also, while social structure for a 
particular community or population can remain stable over multiple 
generations, it is not necessarily a fixed or rigid characteristic for 
a particular population or geography and can change in response to 
changing conditions, such as changes in fishing practices (Ansmann et 
al. 2012).
    Doubtful Sound bottlenose dolphins appear to have a relatively 
unique social structure that includes a large proportion of strong, 
long-lasting associations both within and between sexes (Lusseau et al. 
2003). The community structure also seems more stable over time 
compared to other populations (Lusseau et al. 2003). However, group 
membership was still fluid and thus consistent with a ``fission-
fusion'' model; and, females did display an association pattern similar 
to that of populations elsewhere (Lusseau et al. 2003). Lusseau et al. 
2003 concluded that the most parsimonious explanation of the observed 
social structure is the isolation of the Doubtful Sound community from 
other bottlenose communities. According to this hypothesis, the 
geographic isolation and consequent lack of immigration and emigration, 
promotes the formation of alliances and stability of the overall social 
structure. Lusseau et al. (2003) also hypothesized the stable social 
structure observed in Doubtful Sound could be driven by the temporally 
and spatially variable prey resources within the fiord and a 
requirement for greater cooperation among the dolphins in order to 
forage efficiently. Data to test either of these hypotheses are not 
available. Thus, it is not possible to determine whether the observed 
social structure in Doubtful Sound is a special or unique adaptation in 
response to ecological constraints, or whether it is simply a 
consequence of the community's relative isolation.
    To our knowledge, the only study of social structure for bottlenose 
dolphins within Fiordland comes from the Doubtful Sound community, and 
comparable studies for the remaining fiords appear to be lacking. The 
extent to which the social structure of Doubtful Sound can be 
extrapolated to the other communities is unknown, especially for the 
transient community that occurs in the northern fiords (Boisseau 2003). 
Given the unknown social structure of the other Fiordland communities 
and the uncertainty of whether the observed social structure in 
Doubtful Sound is evolutionarily meaningful, we conclude this 
interesting characteristic of the Doubtful Sound community does not 
qualify the Fiordland population segment as ``significant'' to the 
taxon as a whole.
    The Petitioner discusses the seasonal changes in distribution of 
the Fiordland dolphins in response to water temperature and asserts 
this is relatively unusual behavior. The Petitioner discusses how the 
Fiordland dolphins tend to occupy the warmer waters of the inner fiords 
during the summer calving season; and in winter, when the inner fiord 
waters become colder, the dolphins are found closer to the fiord 
entrances. This seasonal change in habitat use has been documented for 
the dolphin community in Doubtful Sound (Elliott et al. 2011; Henderson 
2013b); however, as discussed in detail previously, it is not 
necessarily the case for the other Fiordland communities (Lusseau 
2005b, Currey et al. 2008c, Henderson 2013b). Furthermore, seasonal 
habitat shifts that are correlated with water temperature are not 
uncommon among coastal bottlenose dolphin populations, especially those 
at higher latitudes (Shane et al. 1986; Wilson et al. 1997). 
Populations at lower-latitudes also show local seasonal changes in 
distribution, which may be in response to factors other than water 
temperature (Shane et al. 1986). Populations in the western Atlantic 
also undergo seasonal migrations that correspond to changes in water 
temperature (Connor et al. 2000). Similar to the females in Doubtful 
Sound, female dolphins elsewhere have also been observed to make use of 
more warmer and more protected areas for calving (Shane et al. 1986; 
Wilson et al. 1997). Overall, we conclude that this particular behavior 
does not help qualify the Fiordland population segment as 
``significant'' to the taxon as a whole.
    In summary, while the Fiordland bottlenose dolphins do exhibit 
differences from bottlenose dolphin populations