Marine mammals feed at a variety of trophic levels, occur from freshwater to openocean ecosystems and are found across virtually all latitudes. Due to their high historical, and sometimes present-day, abundances, capability for large-scale movements and high metabolic rates, they have the potential to affect the structure and function of ecosystems through a variety of mechanisms over both ecological and evolutionary time. Usually, the effects of marine mammals on ecosystems are explicitly or implicitly considered to occur through their ability to remove prey through direct predation. Recent empirical studies and a rich theoretical framework, however, demonstrate that marine mammals can affect ecosystems through more diverse pathways, including those that are driven by marine mammal behaviour. Thus, non-consumptive effects of and on marine mammals may be critical in shaping their ecological importance. Nonconsumptive effects may include risk effects, whereby predators induce costly changes to prey behaviour that impact prey population sizes or the magnitude and spatiotemporal patterns of prey impacts on communities (e.g. behaviour-mediated trophic cascades). Changes in the abundance of large apex predators (both marine mammals and sharks) and the introduction of perceived and real risks (human disturbance) may also affect behaviours of marine mammals and their prey that cascade to the wider ecosystem; the conditions under which such cascading effects might be most important, however, remain poorly understood. Other behaviour-driven ecological roles of marine mammals may include foraging tactics that facilitate the foraging of other species (especially seabirds), translocating nutrients and linking the dynamics of spatially distinct food webs.

/pdf/behavioural-drivers-of-the-ecological-roles-and-importance-4679i1yxzo.pdf

Behavioural drivers of the ecological roles and importance of marine mammals

Social delphinids employ a vocal repertoire of clicks for echolocation and whistles for communication. Conversely, the less social and acoustically cryptic harbour porpoises (Phocoena phocoena) only produce narrow-band high-frequency (NBHF) clicks with properties that appear poorly suited for communication. Nevertheless, these small odontocetes likely mediate social interactions, such as mate choice and mother-calf contact, with sound. Here, we deployed six tags (DTAG3) on wild porpoises in Danish waters for a total of 96 hours to investigate if the patterns and use of stereotyped NBHF click trains are consistent with a communication function. We show that wild porpoises produce frequent (up to 27 $$\bullet $$
 min−1), high-repetition rate click series with repetition rates and output levels different from those of foraging buzzes. These sounds are produced in bouts and frequently co-occur with emission of similar sounds by nearby conspecifics, audible on the tags for >10% of the time. These results suggest that social interactions are more important to this species than their limited social encounters at the surface may indicate and that these interactions are mediated by at least two broad categories of calls composed of short, high-repetition rate click trains that may encode information via the repetition rate of their stereotyped NBHF clicks.

/pdf/click-communication-in-wild-harbour-porpoises-phocoena-1it9bivvlc.pdf

Click communication in wild harbour porpoises (Phocoena phocoena).

As awareness of the effects of anthropogenic noise on marine mammals has grown, research has broadened from evaluating physiological responses, including injury and mortality, to considering effects on behavior and acoustic communication. Most mitigation efforts attempt to minimize injury by enabling animals to move away as noise levels are increased gradually. Recent experiences demonstrate that this approach is inadequate or even counterproductive for small, localized marine mammal populations, for which displacement of animals may itself cause harm. Seismic surveys within the ranges of harbor porpoise Phocoena phocoena in California and Māui dolphin Cephalorhynchus hectori maui in New Zealand highlight the need to explicitly consider biological risks posed by displacement during survey planning, monitoring, and mitigation. Consequences of displacement are poorly understood, but likely include increased stress and reduced foraging success, with associated effects on survival and reproduction. In some cases, such as the Critically Endangered Māui dolphin, displacement by seismic activities risks exposing the re maining 55 dolphins to bycatch in nearby fisheries. Similar concerns about military and industrial activities exist for island-associated species such as melon-headed whales Peponocephala electra in Hawai’i; shelf-break associated species such as Cuvier’s beaked whales Ziphius cavirostris off the US Atlantic coast, and whales foraging in coastal habitats, such as the Critically Endangered western gray whale Eschrichtius robustus. We present an expanded framework for considering disturbance effects that acknowledges scientific uncertainty, providing managers and operators a more robust means of assessing and avoiding potential harm associated with both displacement and direct effects of intense anthropogenic noise exposure.

/pdf/nowhere-to-go-noise-impact-assessments-for-marine-mammal-2pj9hlnw2r.pdf

Nowhere to go: noise impact assessments for marine mammal populations with high site fidelity

Lethal interactions among large vertebrate predators have long interested researchers because of ecological and conservation issues. Research focusing on lethal interactions among vertebrate top predators has used several terms with a broad sense, and also introduced new terminology. We analysed the published literature with reference to the main underlying concepts and the use of terminology and its ecological context. The most frequently used terms in the literature were 'predation', 'intraguild predation', 'interference competition', and 'interspecific killing'. Most studies presented evidence of the killing of the victim (77%), but information regarding its consumption was not given in 48% of cases. More than half of the analysed studies (56%) had no solid information on the degree of competition between interacting species. By reviewing definitions and their underlying assumptions, we demonstrate that lethal interactions among large vertebrate predators could be designated using four terms—'predation', 'intraguild predation', 'interspecific competitive killing', and 'superpredation'—without the need to employ additional terminology that may increase confusion and misuse. For a correct framework of these lethal interactions it is critical to assess if the kill is consumed, if the victim is indeed a competitor of the killer, and if the prey is a high-order predator. However, these elements of the framework are simultaneously the most common constraints to studies of lethal interactions, since they often require a great effort to obtain. The proper use of terms and concepts is fundamental to understanding the causes behind lethal interactions and, ultimately, what is actually happening in these complex interactions.

/pdf/lethal-interactions-among-vertebrate-top-predators-a-review-47wgb230as.pdf

Lethal interactions among vertebrate top predators: a review of concepts, assumptions and terminology.

Common bottlenose dolphins (Tursiops truncatus) are well-known for their overtly aggressive behavior (Herzing et al. 2003, Blomqvist and Amundin 2004, Coscarella and Crespo 2009). Indirect indicators include the prevalence of tooth rake marks on individuals, which have been used to document relative rates of intraspecific antagonism by age, sex, reproductive status and season in these odontocetes (e.g., McCann 1974, Scott et al. 2005). The contexts and causes of intraspecific aggression vary widely, with agonistic interactions arising from social, affiliative behaviors, copulation, coercion, or even as a result of anthropogenic factors (Herzing 1996; Connor et al. 2000a, 2001). When observed directly, these may include head-to-head posturing, acoustic threats, and even physical violence (e.g., body slamming, tail hitting, charging, jawing, and biting) (Herzing 1996, Connor et al. 2000b, Blomqvist and Amundin 2004). Indeed, in one case scenario reported by Parsons et al. (2003), a solo adult male was actually rendered unconscious by two smaller bottlenose rivals (constituting a well-known male alliance) during repeated, violent exchanges. Perhaps the most striking example of targeted intraspecific aggression in these delphinids, however, is the practice of infanticide, as revealed from postmortem examinations of stranded calves (Patterson et al. 1998, Dunn et al. 2002) and from several anecdotal observations at sea (e.g., Wilson, Dunn et al. 2002, Eisfeld 2003). The most detailed and compelling account in the field was recorded by Kaplan et al. (2009) off the coast of Florida from an aerial blimp, and describes a prolonged, 51 min attack on a newborn calf by several adult males that was thought to result in the death of the infant (although this was never actually confirmed). However, direct observations of

Agonistic intraspecific behavior in free‐ranging bottlenose dolphins: Calf‐directed aggression and infanticidal tendencies by adult males

Between 2007 and 2009, we witnessed three aggressive interactions between harbor porpoises and bottlenose dolphins in Monterey Bay, California. This is the first time such aggression has been documented in the Pacific, and the first time a harbor porpoise was collected immediately after witnessing its death, inflicted by bottlenose dolphins. Of the bottlenose dolphins present, 92% were males either confirmed (61%) or putative (31%). Since 2005, 44 harbor porpoise deaths inflicted by bottlenose dolphins were documented in California. Aberrant behavior was rejected as a cause of aggression, based on widespread documentation of similar behaviors in other populations of free-ranging bottlenose dolphins. The evidence for interspecies territoriality as a form of competition for prey was weak: there is little dietary overlap and there are differences in bottlenose dolphin and harbor porpoise distribution patterns in California. Object-oriented play was plausible as a form of practice to maintain intraspecific infanticidal skills or a form of play to maintain fighting skills between male associates. Contributing factors could be high-testosterone levels, as attacks occurred at the height of the breeding season, and/or a skewed operational sex ratio. Ultimately, we need more information about bottlenose dolphin social structure at the time of the aggression.

“Porpicide” in California: Killing of harbor porpoises (Phocoena phocoena) by coastal bottlenose dolphins (Tursiops truncatus)

The prevalence of epidermal conditions in a small population of coastal bottlenose dolphins (Tursiops truncatus) in Monterey Bay was evaluated between 2006 and 2008. Five different skin condition categories were considered, including Pox-Like Lesions, Discoloration, Orange Film, Polygon Lesions, and Miscellaneous Markings. Of 147 adults and 42 calves photographically examined, at least 90 and 71%, respectively, were affected by at least one or multiple conditions. Pox-Like Lesions were the most prevalent, affecting 80% of the population, including adults and calves. This condition warrants the most urgent investigation being possibly indicative of the widespread presence of poxvirus or a similar pathogen in the population. In view of the high number of individuals affected, standard monitoring of the health status of Monterey Bay bottlenose dolphins is considered imperative. Discoloration was strongly associated with Pox-Like lesions. Orange Films were likely an epifaunal infestation caused by diatoms, which have been documented in other cetacean species. Polygon Lesions, a newly described category, could be the result of infestation by barnacles of the genus Cryptolepas. Miscellaneous Markings were variable in appearance and may not have the same causative factor. Although none of the proposed etiologies can be confirmed without appropriate clinical tests, recognizing common visible characteristics of the conditions could aid in preliminary comparisons across populations and individuals.

/pdf/prevalence-of-epidermal-conditions-in-california-coastal-5ev6tvaw87.pdf

Prevalence of Epidermal Conditions in California Coastal Bottlenose Dolphins (Tursiops truncatus) in Monterey Bay

This study provides the first in depth assessment of Sea Otter haul-out patterns in Elkhorn Slough, California and their relationship to environmental variables. Seasonal and daily water and air temperature fluctuations are a good predictor of Sea Otter haul-out patterns but are affected by the availability of haul-out sites at different tide levels. The cost effectiveness of this choice may be maximal at night because of lack of human disturbance. Southern Sea Otters (Enhydra lutris nereis) were observed during 50 bimonthly 24-h periods between August 2007 and July 2009 (n 5 1187 h) from a shore-based observation site located above a non-territorial male resting area on the north side of Moss Landing Harbor. We counted the number of Sea Otters in the area (both in the water and on land) at 30-min intervals. We also recorded tide height, and air and water temperature. Thirty-minute counts averaged 42 Sea Otters using the area (land and water) during the day and 66 at night. The average number of Sea Otters hauled out in the study area during the same haul-out event was 22, and the maximum number was 93. Sea Otters were observed hauled out on 70% of the days surveyed, and the proportion of Sea Otters hauled out was significantly higher at night. Higher numbers of Sea Otters on land was significantly correlated with lower air and water temperature, and with mid-range tide-heights. We speculate that haul- out behavior could play an important role in energy conservation; however, human-related traffic patterns in the area may negatively affect this energy conservation strategy.

/pdf/patterns-of-sea-otter-haul-out-behavior-in-a-california-2asxen8n4z.pdf

Patterns of Sea Otter Haul-Out Behavior in a California Tidal Estuary in Relation to Environmental Variables

Socio-sexual and mating behaviors, to our knowledge, have not been previously documented among free-ranging beluga whales, Delphinapterus leucas, but they have been described in detail for captive belugas. We report on the fi rst photodocumented interaction and display of socio-sexual and apparent mating behavior of noncaptive beluga whales in Cook Inlet, Alaska. This behavior was seen on two different days in the same river mouth in uncharacteristically clear waters of upper Cook Inlet. On 24 April 2014, social and possible mating behaviors were observed and photographed for approximately 12 min within a group of nine adult beluga whales in the mouth of Middle River on the west central side of Cook Inlet. A total of 136 photographs were taken at a radial distance Introduction Socio-sexual behavioral interactions among free-ranging beluga whales, Delphinapterus leucas, have not been previously documented, to our knowledge, and are thus poorly understood. Although mating and social behaviors have been described for captive beluga whales (Hill et al., 2015), it is logistically diffi cult to observe undisturbed behavior among free-ranging beluga. They inhabit remote, and in the case of the Cook Inlet beluga whale (CIBW), typically muddy waters. Observations of socio-sexual behaviors of freeranging CIBW are needed to address critical information gaps on the natural history, mating behavior, and potential behavioral habitat preference of this declining insular population. Little is known about the mating behavior or mating season of beluga whales in the wild. Reported age of sexual maturity varies from 4 to 10 years for females and 8 to 15 years for males (Nowak, 1991; Suydam et al.1). Gestation is 14.0–14.5 months, with a single calf born in late spring or early summer (Sergeant, 1973). This would suggest mating occurs in early spring. In autumn, beluga whale populations migrate toward a few common wintering grounds in Bering Sea offshore waters characterized by unconsolidated pack ice where mating is believed to occur during late winter or early spring (Brodie, 1971; Sergeant, 1973; Brown Gladden et al., 1997). Unlike the Arctic stocks, the Cook Inlet beluga population is not thought 1Suydam, R., J. J. Burns, and G. Carroll. 1999. Age, growth, and reproduction of beluga whales from the eastern Chukchi Sea, Alaska. Paper presented to the Alaska Beluga Whale Committee workshop, March 30–April 1, 1999. 5 p. to undertake seasonal migrations outside of Cook Inlet (Laidre et al., 2000; Rugh et al., 2000). Specifi c breeding areas are unknown or possibly nonexistent (i.e. mating might occur anywhere throughout their range). Similar to Arctic beluga populations, CIBW calving is believed to occur in early summer (Hobbs et al., 2015a) although Native hunters have observed newborn CIBW calves from April through August (Huntington, 2000). Alaska natives described CIBW calving areas as the northern side of Kachemak Bay in April and May, off the Beluga and Susitna River mouths in May, and in Chickaloon Bay and Turnagain Arm during summer (Huntington, 2000). McGuire et al.2, during vessel-based surveys of the upper reaches of Cook Inlet in 2005–07, did not document any specifi c calving locations or a defi nitive calving season and calves were encountered in all surveyed location and months (April– October). Thus CIBW are reported to continue to calve later in the season than the Arctic stocks, although their calving season is unclear. In part, some confusion on calving dates may be a function of sightings of calves well into the summer that were actually born weeks or months earlier. Global observations of both wild and captive beluga whales indicate that breeding is seasonal. Among captive beluga whales, Robeck et al. (2005) reported that both testosterone in males and progesterone in females were elevated during late winter/ear2McGuire, T. L., C. C. Kaplan, M. K. Blees, and M. R. Link. 2008. Photo-identifi cation of beluga whales in upper Cook Inlet, Alaska. 2007 Annu. Rep. Prep. LGL Alaska Res. Assoc., Inc., Anchorage, AK, for Chevron, Natl. Fish Wildl. Found., and ConocoPhillips Alaska, Inc., 52 p. > 500 m. On 7 May 2014, similar behaviors were observed among four adult beluga whales in the same location for about 7 min. The second group was not photo-documented due to fl ight limitations. In both circumstances, affi liative behavioral events such as echelon and contact swimming, and socio-sexual behaviors such as ventrum-toventrum contact, ventral presentations, pelvic thrusting, nodding, and rubbing were observed. These behaviors resemble those previously reported for captive beluga mating behaviors and copulation. Similarities between these observations with captive mating behaviors, and the timing of ovulation and peak calving periods from other wild beluga populations, provide strong evidence that mating occurs during early spring months in Cook Inlet.

Socio-sexual and probable mating behavior of Cook Inlet beluga whales, Delphinapterus leucas, observed from an aircraft

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“Porpicide” in California: Killing of harbor porpoises (Phocoena phocoena) by coastal bottlenose dolphins (Tursiops truncatus)

Prevalence of Epidermal Conditions in California Coastal Bottlenose Dolphins (Tursiops truncatus) in Monterey Bay

Patterns of Sea Otter Haul-Out Behavior in a California Tidal Estuary in Relation to Environmental Variables

Socio-sexual and probable mating behavior of Cook Inlet beluga whales, Delphinapterus leucas, observed from an aircraft