Jeff W. Higdon

How seals divide up the world: environment, life history, and conservation

Pinnipeds display a remarkable variation in life history adaptations while successfully inhabiting almost every marine environment. We explore how they have done this by grouping the world’s pinniped species according to their environmental conditions, mating systems, lactation strategies, and timing of life histories. Next, we tested whether any of these clusters provide information about risk of extinction (using the International Union for Nature and the Conservation of Natural Resources status ranks). Seals at risk were not characterized by differences in lactation pattern (22% short vs. 46% long), mating system (24% multi-male vs. 35% harems), or timing of life history events (23% fast vs. 42% slow) but did differ based on four environmental groupings. Grouping traits (rather than seals) described two clusters: one that included the environmental trait, primary productivity, and a second one that included all other environmental variables (seasonality, latitude, and temperature). Based on this result and theoretical considerations, we plotted seals according to energy (primary productivity) and variation (seasonality) and found a pattern analogous to that of the same four groups determined by cluster analysis of all environmental variables. Of the two pinniped groups representing low variation (equatorial and high productivity), ten of 21 seal species have been designated at risk, in contrast to none of the 13 seal species adapted to high variation. We conclude that seals appear to be best adapted to seasonal environments and thus, conservation efforts may benefit by concentrating on species inhabiting less variable environments.

Prey items and predation behavior of killer whales (Orcinus orca) in Nunavut, Canada based on Inuit hunter interviews

BackgroundKiller whales (Orcinus orca) are the most widely distributed cetacean, occurring in all oceans worldwide, and within ocean regions different ecotypes are defined based on prey preferences. Prey items are largely unknown in the eastern Canadian Arctic and therefore we conducted a survey of Inuit Traditional Ecological Knowledge (TEK) to provide information on the feeding ecology of killer whales. We compiled Inuit observations on killer whales and their prey items via 105 semi-directed interviews conducted in 11 eastern Nunavut communities (Kivalliq and Qikiqtaaluk regions) from 2007-2010.ResultsResults detail local knowledge of killer whale prey items, hunting behaviour, prey responses, distribution of predation events, and prey capture techniques. Inuit TEK and published literature agree that killer whales at times eat only certain parts of prey, particularly of large whales, that attacks on large whales entail relatively small groups of killer whales, and that they hunt cooperatively. Inuit observations suggest that there is little prey specialization beyond marine mammals and there are no definitive observations of fish in the diet. Inuit hunters and elders also documented the use of sea ice and shallow water as prey refugia.ConclusionsBy combining TEK and scientific approaches we provide a more holistic view of killer whale predation in the eastern Canadian Arctic relevant to management and policy. Continuing the long-term relationship between scientists and hunters will provide for successful knowledge integration and has resulted in considerable improvement in understanding of killer whale ecology relevant to management of prey species. Combining scientists and Inuit knowledge will assist in northerners adapting to the restructuring of the Arctic marine ecosystem associated with warming and loss of sea ice.

Killer whale (Orcinus orca) predation in a multi-prey system

Predation can regulate prey numbers but predator behaviour in multiple-prey systems can complicate understanding of control mechanisms. We investigate killer whale (Orcinus orca) predation in an ocean system where multiple marine mammal prey coexist. Using stochastic models with Monte-Carlo simulations, we test the most likely outcome of predator selection and compare scenarios where killer whales: (1) focus predation on larger prey which presumably offer more energy per effort, (2) generalize by feeding on prey as encountered during searches, or (3) follow a mixed foraging strategy based on a combination of encounter rate and prey size selection. We test alternative relationships within the Hudson Bay geographic region, where evidence suggests killer whales seasonally concentrate feeding activities on the large-bodied bowhead whale (Balaena mysticetus). However, model results indicate that killer whales do not show strong prey specialization and instead alternatively feed on narwhal (Monodon monoceros) and beluga (Delphinapterus leucas) whales early and late in the ice-free season. Evidence does support the conjecture that during the peak of the open water season, killer whale predation can differ regionally and feeding techniques can focus on bowhead whale prey. The mixed foraging strategy used by killer whales includes seasonal predator specialization and has management and conservation significance since killer whale predation may not be constrained by a regulatory functional response.

Sustained disruption of narwhal habitat use and behavior in the presence of Arctic killer whales

Significance Predators are widely understood to impact the structure and stability of ecosystems. In the Arctic, summer sea ice is rapidly declining, degrading habitat for Arctic species, such as polar bears and ringed seals, but also providing more access to important predators, such as killer whales. Using data from concurrently tracked predator (killer whales) and prey (narwhal), we show that the presence of killer whales significantly changes the behavior and distribution of narwhal. Because killer whales are effective predators of many marine mammals, similar predator-induced changes would be expected in the behavior of tracked animals in marine ecosystems worldwide. However, these effects are rarely considered and may frequently go unrecognized. Although predators influence behavior of prey, analyses of electronic tracking data in marine environments rarely consider how predators affect the behavior of tracked animals. We collected an unprecedented dataset by synchronously tracking predator (killer whales, N = 1; representing a family group) and prey (narwhal, N = 7) via satellite telemetry in Admiralty Inlet, a large fjord in the Eastern Canadian Arctic. Analyzing the movement data with a switching-state space model and a series of mixed effects models, we show that the presence of killer whales strongly alters the behavior and distribution of narwhal. When killer whales were present (within about 100 km), narwhal moved closer to shore, where they were presumably less vulnerable. Under predation threat, narwhal movement patterns were more likely to be transiting, whereas in the absence of threat, more likely resident. Effects extended beyond discrete predatory events and persisted steadily for 10 d, the duration that killer whales remained in Admiralty Inlet. Our findings have two key consequences. First, given current reductions in sea ice and increases in Arctic killer whale sightings, killer whales have the potential to reshape Arctic marine mammal distributions and behavior. Second and of more general importance, predators have the potential to strongly affect movement behavior of tracked marine animals. Understanding predator effects may be as or more important than relating movement behavior to resource distribution or bottom-up drivers traditionally included in analyses of marine animal tracking data.

Dietary habits of polar bears in Foxe Basin, Canada: possible evidence of a trophic regime shift mediated by a new top predator.

Abstract Polar bear (Ursus maritimus) subpopulations in several areas with seasonal sea ice regimes have shown declines in body condition, reproductive rates, or abundance as a result of declining sea ice habitat. In the Foxe Basin region of Nunavut, Canada, the size of the polar bear subpopulation has remained largely stable over the past 20 years, despite concurrent declines in sea ice habitat. We used fatty acid analysis to examine polar bear feeding habits in Foxe Basin and thus potentially identify ecological factors contributing to population stability. Adipose tissue samples were collected from 103 polar bears harvested during 2010–2012. Polar bear diet composition varied spatially within the region with ringed seal (Pusa hispida) comprising the primary prey in northern and southern Foxe Basin, whereas polar bears in Hudson Strait consumed equal proportions of ringed seal and harp seal (Pagophilus groenlandicus). Walrus (Odobenus rosmarus) consumption was highest in northern Foxe Basin, a trend driven by the ability of adult male bears to capture large‐bodied prey. Importantly, bowhead whale (Balaena mysticetus) contributed to polar bear diets in all areas and all age and sex classes. Bowhead carcasses resulting from killer whale (Orcinus orca) predation and subsistence harvest potentially provide an important supplementary food source for polar bears during the ice‐free period. Our results suggest that the increasing abundance of killer whales and bowhead whales in the region could be indirectly contributing to improved polar bear foraging success despite declining sea ice habitat. However, this indirect interaction between top predators may be temporary if continued sea ice declines eventually severely limit on‐ice feeding opportunities for polar bears.

Observations of killer whales (Orcinus orca) in the Canadian Beaufort Sea

Sightings of killer whales ( Orcinus orca ) are increasing in the eastern Canadian Arctic, but trends in the western Arctic have not been thoroughly examined. We summarise killer whale observations from the Canadian Beaufort Sea, primarily from traditional ecological knowledge interviews and group workshops conducted in 1993 and 2006–2007. After correcting for duplicative reports, we documented 31 observations occurring from the 1940s to 2000s (18 of the 31 observations could be attributed to a particular decade whereas others could not). Killer whales are rare in the Canadian Beaufort Sea, with only 1–5 reported sightings per decade since the 1940s (median = 3). In 1993 only 15% of Inuvialuit hunters in three communities had observed them, including some sightings in Alaska. Recent mapping workshops (2006–2007) collected only eight sightings from 128 participants in all six regional communities. Local observations indicate no apparent increase in killer whale presence in the western Canadian Arctic. Sightings were widely distributed across the region, although concentrated in the Mackenzie Delta area with few to the east. Killer whales are annually observed as far north as Barrow, Alaska, but do not appear to make regular eastward movements and are rare in Canadian waters.

Beluga whale summer habitat associations in the Nelson River estuary, western Hudson Bay, Canada

To understand beluga whale (Delphinapterus leucas) estuarine use in the Nelson River estuary, southwest Hudson Bay, we recorded and examined beluga movements and habitat associations for the July through August period in 2002–2005. We compared locations of belugas fitted with satellite transmitters (“tags”) (2002–2005) and aerial-surveyed (2003 and 2005) belugas for years of differing freshwater flow from the Nelson River which is influenced by hydroelectric activity. Using the beluga telemetry location data, we estimated an early August behavioral shift in beluga distribution patterns from local estuarine use to a progressively more migratory behavior away from the estuary. The timing of this shift in behavior was also apparent in results of beluga aerial surveys from the 1940s–1960s, despite environmental changes including later freeze-up and warming ocean temperatures. Overall, during the higher than average discharge (“wet”) year of 2005, the three tagged belugas ranged farther from the Nelson River but not farther from the nearest shore along southwestern Hudson Bay, compared to the 10 tagged belugas tracked during the “dry” years of 2002–2004 with below average discharges. Aerial survey data for 2003 and 2005 display a similar dry vs. wet year shift in spatial patterns, with no significant change in overall density of belugas within the study area. In the Nelson estuary, proximity to the fresh-salt water mixing area may be more important than the shallow waters of the upper estuary. Killer whales (Orcinus orca) were observed in the Churchill area (200 km northwest) during each year of study, 2002–05, and belugas may benefit from the proximity to shallow estuary waters that provide protection from the larger-bodied predator. Study results contribute to an understanding of the influence of environmental variation on how and why belugas use estuaries although considerable uncertainties exist and additional research is required.

Evidence of molting and the function of “rock-nosing” behavior in bowhead whales in the eastern Canadian Arctic

Bowhead whales (Balaena mysticetus) have a nearly circumpolar distribution, and occasionally occupy warmer shallow coastal areas during summertime that may facilitate molting. However, relatively little is known about the occurrence of molting and associated behaviors in bowhead whales. We opportunistically observed whales in Cumberland Sound, Nunavut, Canada with skin irregularities consistent with molting during August 2014, and collected a skin sample from a biopsied whale that revealed loose epidermis and sloughing. During August 2016, we flew a small unmanned aerial system (sUAS) over whales to take video and still images to: 1) determine unique individuals; 2) estimate the proportion of the body of unique individuals that exhibited sloughing skin; 3) determine the presence or absence of superficial lines representative of rock-rubbing behavior; and 4) measure body lengths to infer age-class. The still images revealed that all individuals (n = 81 whales) were sloughing skin, and that nearly 40% of them had mottled skin over more than two-thirds of their bodies. The video images captured bowhead whales rubbing on large rocks in shallow, coastal areas—likely to facilitate molting. Molting and rock rubbing appears to be pervasive during late summer for whales in the eastern Canadian Arctic.

Reports of Humpback and Minke Whales in the Hudson Bay Region, Eastern Canadian Arctic

Abstract We summarize recently reported sightings of Megaptera novaeangliae (Humpback Whales) and Balaenoptera acuturostrata (Minke Whales) in the Hudson Bay region, in the eastern Canadian Arctic. Balaena mysticetus (Bowhead Whale) is the only baleen whale historically known from Hudson Bay, and during the commercial whaling era (1860–1915), no other large whale was reported to occur there. We note recent (ca. last 10 years) Humpback observations reported by local Inuit hunters in Hudson Bay and northern Foxe Basin. One Humpback was also observed by cetacean biologists in Ungava Bay during an aerial survey for Delphinapterus leucas (Beluga Whales). Minke Whales have previously been reported in southern Hudson Bay and James Bay, and recent discussions with Inuit hunters have indicated possible sightings in Foxe Basin and western Hudson Bay. They are commonly observed by Inuit in eastern Hudson Strait, where there have also been recent detections by biologists. Observations of these species in Hudson Bay and Foxe Basin may be related to reduced ice cover and increased open water, changes in prey species distributions, population recovery and growth following commercial whaling, or some combination of factors. More efficient reporting of observations is needed, and improved community-level monitoring would assist with documentation of temperate-region species in high-latitude areas.

Global Warming and Arctic Marine Mammals (GWAMM)

The GWAMM project has developed a Community-Based Monitoring (CBM) network within the greater Hudson Bay region. Our goal was to monitor marine ecosystem change using apex predators but also to understand the drivers of change. Results provided policy information required to allow northerners the ability to adapt to the environmental changes. During the Inuit subsistence hunts of 2007, the network relied on Arviat and Sanikiluaq community involvement. In 2008 and 2009, we expanded the network to include the communities of Repulse Bay and Igloolik, respectively. Partnering with northerners provided whale and seal tissue samples from hunts as well as a collection of prey species representing parts of the marine environment. A reference collection of samples from the complete food web was developed and used to build a model of trophic interactions from marine mammals down to nutrients and phytoplankton. GWAMM is also a network project that links to other marine mammal research projects in the region including satellite-telemetry movement studies of polar bears, seals, and whales, and photo-identification of bowhead and killer whales, and use of chemical signals to understand whale and seal diet, and tracking predation effects caused by invasive species such as killer whales. Results indicated that with declining sea ice, the Hudson Bay marine ecosystem is shifting from a polar bear-seal system with Inuit hunters at the apex to one dominated by cetaceans with killer whales at the apex. This shift is eroding Inuit traditional subsistence culture. As a result, our project has the added goal to provide northerners with information required to adapt to a rapidly changing world where Arctic marine mammal populations are showing demographic strain due to polar warming.