The giant anteater (Myrmecophaga tridactyla) ranges widely in northern South America and southern Central America, where its main predators are jaguars (Panthera onca) and pumas (Puma concolor). The ...species' bold color pattern has been attributed to predator avoidance through both aposematism and disruptive camouflage. Its powerful front claws can be used not only for ripping open ant and termite nests but also as a lethal defense against attacking jaguars (and humans!); this has led to the suggestion that the conspicuous black "bracelets" on its forelimbs could be an aposematic warning signal to potential predators. After photographing this unaccompanied pair of giant anteaters in the Brazilian Pantanal in September 2022, we suggest another function for their distinctive coloration -- mimicry. The forelimb "bracelets" create a panda-like pattern with a black nose, eyepatch, and ear. The paleness of the anteater's near forelimb extends up and back toward its rump, creating the visual impression of an upper body of another animal. The pale inner side of the anteater's far forelimb makes it appear to be a near forelimb, adding to the illusion of a separate, smaller animal.
With coverage on all the marine mammals of the world, authors Jefferson, Webber, and Pitman have created a user-friendly guide to identify marine mammals alive in nature (at sea or on the beach), ...dead specimens "in hand", and also to identify marine mammals based on features of the skull. This handy guide provides marine biologists and interested lay people with detailed descriptions of diagnostic features, illustrations of external appearance, beautiful photographs, dichotomous keys, and more. Full color illustrations and vivid photographs of every living marine mammal species are incorporated, as well as comprehendible maps showing a range of information. For readers who desire further consultation, authors have included a list of literature references at the end of each species account. For an enhanced understanding of habitation, this guide also includes recognizable geographic forms described separately with colorful paintings and photographs. All of these essential tools provided make Marine Mammals of the World the most detailed and authoritative guide available!* Contains superb photographs of every species of marine mammal for accurate identification * Authors' collective experience adds up to 80 years, and have seen nearly all of the species and distinctive geographic forms described in the guide * Provides the most detailed and anatomically accurate illustrations currently available * Special emphasis is placed on the identification of species in "problem groups, " such as the beaked whales, long-beaked oceanic dolphin, and southern fur seals * Includes a detailed list of sources for more information at the back of the book.
This paper is part of a comprehensive review of the oceanography of the eastern tropical Pacific, the oceanic region centered on the eastern Pacific warm pool, but also including the equatorial cold ...tongue and equatorial current system, and summarizes what is known about oceanographic influences on seabirds and cetaceans there. The eastern tropical Pacific supports on the order of 50 species of seabirds and 30 species of cetaceans as regular residents; these include four endemic species, the world's largest populations for several others, three endemic sub-species, and a multi-species community that is relatively unique to this ecosystem. Three of the meso-scale physical features of the region are particularly significant to seabirds and cetaceans: the Costa Rica Dome for blue whales and short-beaked common dolphins, the Equatorial Front for planktivorous seabirds, and the countercurrent thermocline ridge for flocking seabirds that associate with mixed-species schools of spotted and spinner dolphins and yellowfin tuna. A few qualitative studies of meso- to macro-scale distribution patterns have indicated that some seabirds and cetaceans have species-specific preferences for surface currents. More common are associations with distinct water masses; these relationships have been quantified for a number of species using several different analytical methods. The mechanisms underlying tropical species-habitat relationships are not well understood, in contrast to a number of higher-latitude systems. This may be due to the fact that physical variables have been used as proxies for prey abundance and distribution in species-habitat research in the eastern tropical Pacific. Though seasonal and interannual patterns tend to be complex, species-habitat relationships appear to remain relatively stable over time, and distribution patterns co-vary with patterns of preferred habitat for a number of species. The interactions between seasonal and interannual variation in oceanographic conditions with seasonal patterns in the biology of seabirds and cetaceans may account for some of the complexity in species-habitat relationship patterns. Little work has been done to investigate effects of El Nino-Southern Oscillation cycles on cetaceans, and results of the few studies focusing on oceanic seabirds are complex and not easy to interpret. Although much has been made of the detrimental effects of El Nino events on apex predators, more research is needed to understand the magnitude, and even direction, of these effects on seabirds and cetaceans in space and time.
Currently, there are three recognized ecotypes (or species) of killer whales (Orcinus orca) in Antarctic waters, including type B, a putative prey specialist on seals, which we refer to as “pack ice ...killer whale” (PI killer whale). During January 2009, we spent a total of 75.4 h observing three different groups of PI killer whales hunting off the western Antarctic Peninsula. Observed prey taken included 16 seals and 1 Antarctic minke whale (Balaenoptera bonaerensis). Weddell seals (Leptonychotes weddellii) were taken almost exclusively (14/15 identified seal kills), despite the fact that they represented only 15% of 365 seals identified on ice floes; the whales entirely avoided taking crabeater seals (Lobodon carcinophaga; 82% relative abundance) and leopard seals (Hydrurga leptonyx; 3%). Of the seals killed, the whales took 12/14 (86%) off ice floes using a cooperative wave‐washing behavior; they produced 120 waves during 22 separate attacks and successfully took 12/16 (75%) of the Weddell seals attacked. The mean number of waves produced per successful attack was 4.1 (range 1–10) and the mean attack duration was 30.4 min (range 15–62). Seal remains that we examined from one of the kills provided evidence of meticulous postmortem prey processing perhaps best termed “butchering.”
Long‐distance migration in whales has historically been described as an annual, round‐trip movement between high‐latitude, summer feeding grounds, and low‐latitude, winter breeding areas, but there ...is no consensus about why whales travel to the tropics to breed. Between January 2009 and February 2016, we satellite‐tagged 62 antarctic killer whales (Orcinus orca) of four different ecotypes, of which at least three made short‐term (6–8 weeks), long‐distance (maximum 11,000 km, round trip), essentially nonstop, migrations to warm waters (SST 20°C–24°C), and back. We previously suggested that antarctic killer whales could conserve body heat in subfreezing (to −1.9°C) waters by reducing blood flow to their skin, but that this might preclude normal (i.e., continuous) epidermal molt, and necessitate periodic trips to warm waters for routine skin maintenance (“skin molt migration,” SMM). In contrast to the century‐old “feeding/breeding” migration paradigm, but consistent with a “feeding/molting” hypothesis, the current study provides additional evidence that deferred skin molt could be the main driver of long‐distance migration for antarctic killer whales. Furthermore, we argue that for all whales that forage in polar latitudes and migrate to tropical waters, SMM might also allow them to exploit rich prey resources in a physiologically challenging environment and maintain healthy skin.
Reports of killer whales (Orcinus orca) preying on large whales have been relatively rare, and the ecological significance of these attacks is controversial. Here we report on numerous observations ...of killer whales preying on neonate humpback whales (Megaptera novaeangliae) off Western Australia (WA) based on reports we compiled and our own observations. Attacking killer whales included at least 19 individuals from three stable social groupings in a highly connected local population; 22 separate attacks with known outcomes resulted in at least 14 (64%) kills of humpback calves. We satellite‐tagged an adult female killer whale and followed her group on the water for 20.3 h over six separate days. During that time, they attacked eight humpback calves, and from the seven known outcomes, at least three calves (43%) were killed. Overall, our observations suggest that humpback calves are a predictable, plentiful, and readily taken prey source for killer whales and scavenging sharks off WA for at least 5 mo/yr. Humpback “escorts” vigorously assisted mothers in protecting their calves from attacking killer whales (and a white shark, Carcharodon carcharias). This expands the purported role of escorts in humpback whale social interactions, although it is not clear how this behavior is adaptive for the escorts.
Although Hubbs' beaked whale (Mesoplodon carlhubbsi) was previously known from over 60 strandings on both sides of the North Pacific, it had been identified alive in the wild only once, off Oregon in ...1994. In September 2021, we conducted a search effort for beaked whales off the coast of Oregon using a towed hydrophone array and a visual search team. Approximately 350 km off the Columbia River mouth, we detected the vocalizations of an unidentified mesoplodont whale; we stopped our vessel and waited in the area until two unidentified juvenile Mesoplodon surfaced and stayed near our vessel for almost 2 hr. During that time, we took numerous photographs and videos, made behavioral observations, and recorded their vocalizations. The DNA sequence from a biopsy sample identified them as M. carlhubbsi. In this paper, we discuss our biological observations, including color patterning and acquired markings, behavioral observations, and describe for the first time the acoustic characteristics of this species. We confirm that M. carlhubbsi is the source of a previously unidentified acoustic signal known as BW37V, and we update what is known about the at‐sea distribution of this species based on previous recordings and observational records.
For over a century, the Ross Sea killer whale (RSKW;
Orcinus orca
, Antarctic type C), a fish-eating ecotype, has been commonly reported in McMurdo Sound (McM), Ross Sea, Antarctica. However, a ...significant population decline reported at Ross Island after 2006 has been linked to a commercial fishery that began in the Ross Sea in 1996–1997 and targets large Antarctic toothfish (
Dissostichus mawsoni
)—the presumed primary prey of RSKW. We assessed RSKW population abundance and trends using photo-identification data collected in McM during seven summers from 2001–2002 to 2014–2015. We identified 352 individual RSKWs and estimated an average annual population of 470 distinctly marked whales. Using a Bayesian mark–recapture model, we identified two population clusters: ‘regulars’ showed strong inter- and intra-annual site fidelity and an average annual abundance of 73 distinctive individuals (95% probability: 57–88); ‘irregulars’ were less frequently encountered but comprised a larger population with an annual estimate of 397 distinctive individuals (287–609). The number of seasonally resident regulars appeared to be stable over the period of purported RSKW decline, with the estimated annual number of deaths (6; 95% probability: 1–22) offset by the number of recruits (6; 2–19). As an alternative to the decline-due-to-fishery hypothesis, we suggest that the presence of mega-iceberg B-15 at Ross Island during the “iceberg years” (2000–2001 to 2005–2006) could have temporarily disrupted normal RSKW movement patterns, resulting in an
apparent
decline. Continued population monitoring of toothfish and their predators will be important for assessing ecosystem impacts of commercial fishing in the Ross Sea.
The fish‐eating, type‐C ecotype, killer whale is a top predator in the Ross Sea, Antarctica. Increasing knowledge of this animal's foraging habitats, diet and movement patterns is listed amongst the ...research priorities adopted under the framework of the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR).
To contribute to this goal, satellite transmitters were deployed on 10 type‐C killer whales and skin biopsies were obtained from seven individuals in Terra Nova Bay (Ross Sea) during austral summer (January–February) 2015. Hierarchical switching state–space models (hSSSM) were applied to Argos satellite tracking data to describe the movements of tagged whales, which were then paired with available diving data. Stable isotopes analyses were performed on the biopsy samples to describe the diet.
A total of 8,803 Argos locations were available to fit the hSSSM. All whales engaged in potential foraging activity in localized areas along the Ross Sea coastline, followed by uninterrupted travel (i.e. migration) outside Antarctic waters, with no evidence of foraging activity. The pattern of deeper dives matched the occurrence of encamped behaviour indicated by the hSSSM results. The stable isotopes analysis indicated that Antarctic toothfish comprised the largest component (35%) of the prey biomass, raising concerns since this species is targeted by commercial fishery in the Ross Sea Region.
These results provide new insights into the ecology of type‐C killer whales in the Ross Sea Region, underlining a potential threat from commercial fishing in the area. Considering the recent establishment of the Ross Sea Region Marine Protected Area, these findings will contribute to the required Research and Monitoring Programme of the Marine Protected Area and provide new empirical evidence to inform conservation measures in the existing Terra Nova Bay Antarctic Special Protected Area.
•Effort-weighted study of 'postmortem attentive behaviour' (PAB) in cetaceans.•Dolphins (Delphinidae) accounted for 92.3% of 78 PAB records, baleen whales 1.3%.•Encephalisation was an important ...predictor of PAB across taxa.•Female PAB towards dead calves (75%) may have been rescue attempts or grieving.•Male PAB was rare and possibly not caregiving.
The scientific study of death across animal taxa—comparative thanatology—investigates how animals respond behaviourally, physiologically and psychologically to dead conspecifics, and the processes behind such responses. Several species of cetaceans have been long known to care for, attend to, be aroused by, or show interest in dead or dying individuals. We investigated patterns and variation in cetacean responses to dead conspecifics across cetacean taxa based on a comprehensive literature review. We analysed 78 records reported between 1970 and 2016, involving 20 of the 88 extant cetacean species. We adopted a weighted comparative approach to take observation effort into account and found that odontocetes (toothed cetaceans) were much more likely than mysticetes (baleen whales) to attend to dead conspecifics. Dolphins (Delphinidae) had the greatest occurrence of attentive behaviour (92.3% of all records), with a weighed attendance index 18 times greater than the average of all other cetacean families. Two dolphin genera, Sousa and Tursiops, constituted 55.1% of all cetacean records (N=43) and showed the highest incidence of attentive behaviour. Results of analyses intended to investigate the reasons behind these differences suggested that encephalisation may be an important predictor, consistent with the "social brain" hypothesis. Among attending individuals or groups of known sex (N=28), the majority (75.0%) were adult females with dead calves or juveniles (possibly their own offspring, with exceptions), consistent with the strong mother-calf bond, or, in a few cases, with the bond between mothers and other females in the group. The remaining records (25.0%) involved males either showing sexual interest in a dead adult or subadult, or carrying a dead calf in the presence of females. Because an inanimate individual is potentially rescuable, responses to dead conspecifics—especially by females—can be explained at least in part by attempts to revive and protect, having a clear adaptive value. In some cases such responses are followed by apparently maladaptive behaviour such as the long-term carrying of, or standing by, a decomposed carcass, similar to observations of certain terrestrial mammals. Among the possible explanations for the observed cetacean behavioural responses to dead conspecifics are strong attachment resulting in a difficulty of "letting go"—possibly related to grieving—or perhaps individuals failing to recognise or accept that an offspring or companion has died. Our current understanding is challenged by small sample size, incomplete descriptions, and lack of information on the physiology and neural processes underpinning the observed behaviour. We provide research recommendations that would improve such understanding.
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