Stephen J. Insley

Mother-offspring separation and acoustic stereotypy : a comparison of call morphology in two species of Pinnipeds

I have compared structural variation of the primary vocalizations used between mother-offspring pairs in two species of pinnipeds that differ fundamentally in their breeding behaviour: northern elephant seal (Mirounga angustirostris) mothers and offspring normally are together throughout the nursing period; northern fur seal (Callorhinus ursinus) females regularly separate from their offspring while nursing. Two predictions were tested: (1) these vocalizations should be individually-distinct (stereotyped) in females and pups of both species if they serve to function for recognition, and (2) because individuality should be more pronounced in a species where separations and reunions are common, the vocalizations used between northern fur seal mother-offspring pairs should be more individually-stereotyped than those of the northern elephant seal. Principal components analyses revealed structural differences between the calls of females and pups in both species. Analysis of variance showed the calls of individual seals to be acoustically distinct in all cases. The calls used between mother-offspring pairs of northern fur seals were more stereotyped than those of northern elephant seals. These calls had less within-individual variation, greater among-individual variation and were more often correctly predicted in discriminant analyses. The results indicate that selective pressure to develop vocal recognition exists in both species but is greater in the northern fur seal.

Sex differences in razorbill Alca torda parent-offspring vocal recognition.

SUMMARY We investigated differences in parent—offspring vocal recognition between males and females in a natural population of razorbills Alca torda, a long-lived and highly social species of auk (Family: Alcidae). Razorbills provide biparental care to their chicks while at the nest site, after which the male is the sole caregiver for an additional period at sea. Parent—offspring recognition in razorbills is most challenging once the chick becomes mobile, leaves the nest site and goes to sea with the male parent. It is during this period when selection pressure acting on recognition behaviour is expected to be strongest. As a result, we predicted that parent—offspring recognition would be better developed in the male parent, that is, show a paternal bias. To test this prediction we used vocal playback experiments conducted on breeding razorbills at the Gannet Islands, Labrador, Canada. We found (1) most positive responses to playbacks (vocal and phonotactic) occurred close to fledging, (2) males responded more to calls from their chicks than to calls from strange chicks, (3) females responded indifferently to calls from their own or strange chicks and (4) chicks responded more to calls from their male parent than to calls from other adult males. The results provide clear evidence of mutual vocal recognition between the male parent and the chick but not between the female parent and the chick, supporting the prediction that parent—offspring recognition is male biased in this species. Such a bias could have important social implications for a variety of behavioural and basic life history traits such as cooperation and sex-biased dispersal.

Do male northern elephant seals recognize individuals or merely relative dominance rank

Vocal recognition was tested in a socially dynamic context where many individuals interact: the female defense polygyny practiced by male northern elephant seals. The goal was to tease apart whether animals recognize other individuals or instead use a simple rule-based category (i.e., relative dominance rank). A total of 67 playback experiments conducted with 18 males at Año Nuevo State Reserve, California, tested three aspects of recognition: (1) recognition of relative rank; (2) whether such recognition was continuous or categorical; and (3) recognition of familiarity. Results indicate that males recognize familiar individuals although responses are primarily based on relative dominance rank.

Potential impacts of shipping noise on marine mammals in the western Canadian Arctic

As the Arctic warms and sea ice decreases, increased shipping will lead to higher ambient noise levels in the Arctic Ocean. Arctic marine mammals are vulnerable to increased noise because they use sound to survive and likely evolved in a relatively quiet soundscape. We model vessel noise propagation in the proposed western Canadian Arctic shipping corridor in order to examine impacts on marine mammals and marine protected areas (MPAs). Our model predicts that loud vessels are audible underwater when >100km away, could affect marine mammal behaviour when within 2km for icebreakers vessels, and as far as 52km for tankers. This vessel noise could have substantial impacts on marine mammals during migration and in MPAs. We suggest that locating the corridor farther north, use of marine mammal observers on vessels, and the reduction of vessel speed would help to reduce this impact.

Source levels of northern elephant seal vocalizations in‐air

Accurate measurements of vocalization sound‐pressure levels are necessary to determine the acoustical active space of animals in natural and human‐altered ambient noise conditions. Despite this basic need, such data are limited or nonexistent for most species. Our study characterized aerial ambient noise and vocalization source levels for northern elephant seals during the breeding season. Subjects were adult males, lactating females, and dependent offspring (pups) at Ano Nuevo State Reserve. Source level measurements were made using a Type 1 sound level meter and calibrated microphones on‐axis: (1) at 1 m; (2) at several known distances (laser measured); and (3) simultaneously at 1 m and a second known distance. Concurrent ambient noise conditions were measured in situ (non‐weighted 5 min Leq integrated averages) and recorded for later spectral analysis. Measurements were made at two sites, one relatively noisy and the other relatively quiet, to determine whether animals compensate for higher noise condi...

Seasonal patterns in acoustic detections of marine mammals near Sachs Harbour, Northwest Territories

The Arctic is changing rapidly, leading to changes in habitat availability and increased anthropogenic disturbance. Information on the distribution of animals is needed as these changes occur. We examine seasonal presence of marine mammals in the western Canadian Arctic near Sachs Harbour, Northwest Territories, using passive acoustic monitoring between 2015 and 2016. We also examined the influence of environmental variables (ice concentration and distance, wind speed) on the presence of these species. Both bowhead whales (Balaena mysticetus) and beluga whales (Delphinapterus leucas) arrived in late April, and belugas departed in mid-August, while bowheads departed in late October. Bearded seal (Erignathus barbatus) vocalizations began in October, peaked from April through June, and stopped in early July. Ringed seals (Pusa hispida) vocalized occasionally in all months, but were generally quiet. Whales migrated in as the ice broke up and migrated out before ice formed in the autumn. Bearded seals started ...

Acoustic monitoring of northern fur seals in the Bering Sea

A substantial problem in determining whether anthropogenic noise affects marine animals is measuring how an animal responds to a noise source that is located in a remote pelagic environment and is ephemeral in nature. We are interested in measuring northern fur seal reactions to ship noise in the Bering Sea, Alaska, where the fur seals have started to decline. The timing of their decline coincides with an increased probability of interaction with the pollock fishing fleet. Whether fishing activity affects fur seal behavior, via direct competition for fish and/or indirect competition (e.g., acoustic disturbance or vessel avoidance), is unknown and difficult to study. We began by developing procedural tools to measure encounter rates and animal response. We deployed acoustic dataloggers on lactating females in order to monitor for ship signatures. This was referenced to movement data from satellite position fixes and pressure data from dive records. The combined dataset provides assays that measure an animal’s movement (i.e., direction, speed, and relative effort via stroke rate), its overall activity budget (i.e., traveling, diving, and resting), and the pattern of diving behavior. The assays are now being field tested with a new set of instrument deployments during the 2004 fur seal breeding season.

A study of sonic boom effects on seals breeding on Sable Island, Canada

Researchers were on Sable Island, Canada (440°N, 600°W), for the 1997 grey seal (Halichoerus grypus) breeding season to study the affects of sonic booms on seal behavior. The physical parameters of 36 sonic booms associated with the Concorde’s trans‐Atlantic flights were recorded. The average minimum overpressure was −0.568 PSF and mean maximum overpressure was 0.935 PSF. Data were collected on frequency of aggression, movements, and distances moved in 10‐min periods before and after booms to detect changes in general agitation of pups and adults. The number of mother‐pup pairs nursing and number of nursing bouts interrupted during the minute of sonic booms were compared to those in randomly chosen minutes to measure immediate startle responses of seals. There was no difference in the behavior of adults nor pups between 10‐min periods before and after booms, nor did their behavior differ in the minute of booms when compared to randomly chosen control minutes. Female heart rates did not vary before, during...

Multi-Year Counts of Sea Ducks and Gulls In the Nearshore of the Pribilof Islands, Alaska

Abstract Monitoring avian populations over both the reproductive and non-reproductive seasons is required to better understand population changes. Obtaining baseline data in remote sites, however, is often difficult during the non-breeding season, especially in ice-driven ecosystems. We determined annual changes in numbers of over-wintering sea duck and large-bodied gull species and identified their main areas of concentration at one of the Pribilof Islands (St. Paul) in the Bering Sea. Formally trained local citizens undertook weekly counts using standardized methods over 3 non-breeding seasons (2008–2009; 2009–2010; 2010–2011) from late autumn to early spring. Sea ducks and large-bodied gulls were present nearshore in considerable numbers from November to January, and maximum counts usually occurred between February and March when sea-ice cover is at its maximum near the Pribilof Islands. We found that one-time counts would underestimate some species (Bufflehead, King Eider, Harlequin Duck), their numbers having peaked earlier in the non-breeding season. Across years, Harlequin Duck (47% occurrence; maximum of 476 total individuals at all sites), Long-tailed Duck (23%; maximum of 627) and King Eider (18%; maximum of 136) were the most common and abundant species. Buffleheads (maximum of 24 individuals) and White-winged Scoters (maximum of 500 individuals) were less common (<5% occurrence), and had distinctive localized distributions in intertidal and lagoon habitats. Only Harlequin Ducks and large-bodied gulls varied annually, with nearly twice as many birds in 2011 as in 2008. Large-bodied gull concentrations (maximum of 1230 individuals; primarily Glaucous-winged Gulls) were mostly associated with dockside and outfall fish offal rather than landfill. Given that large-bodied gulls foraged in the same sites and monthly peaks mirrored those of sea ducks, kleptoparasitism is a potential problem, especially in absence of fishery discards. Our study fills a gap in the current understanding of regional waterfowl and large-bodied gull status during the non-breeding season in the Pribilof Islands, an important over-wintering location.

Directionality of male northern elephant seal (Mirounga angustirostris) threat calls and how it influences receiver behavior.

Many animal sounds are directional in which the sound energy is focused in a direction that depends on the signaler’s orientation. In the 1970s, Ron Schusterman quantitatively showed this in barking California sea lions and dogs. Several investigators have suggested ways that such features might be particularly useful among individuals in acoustic communication networks. However, only a few have tested such hypotheses experimentally and even fewer have investigated how directional signals affect receiver behavior. In this study, we measured directivity patterns of male northern elephant seal threat calls and used an acoustic playback approach to determine how call directionality influenced the responses of male seals in reproductive competition. We collected data on adult and older subadult seals on a breeding rookery (Ano Nuevo State Park) over three field seasons. Threat calls had substantial directionality, particularly at frequencies above 1 kHz and responses to playbacks depended on call directivity ...