Noise exposure from commercial shipping for the southern resident killer whale population.

This study assesses vessel-noise exposure levels for Southern Resident Killer Whales (SRKW) in the Salish Sea. Kernel Density Estimation (KDE) was used to delineate SRKW summer core areas. Those areas were combined with the output of a regional cumulative noise model describing sound level variations generated by commercial vessels (1/3-octave-bands from 10 Hz to 63.1 kHz). Cumulative distribution functions were used to evaluate SRKW's noise exposure from 15 vessel categories over three zones located within the KDE. Median cumulative noise values were used to group categories based on the associated exposure levels. Ferries, Tugboats, Vehicle Carriers, Recreational Vessels, Containers, and Bulkers showed high levels of exposure (Leq-50th > 90 dB re 1 µPa) within SRKW core areas. Management actions aiming at reducing SRKW noise exposure during the summer should target the abovementioned categories and take into consideration the spatial distribution of their levels of exposure, their mechanical and their operational characteristics.

Development of sociality and emergence of independence in a killer whale (Orcinus orca) calf from birth to 36 months.

Dolphin calves spend most of their time swimming with their mother immediately after birth. As they mature, the calves become increasingly independent, and begin to interact more often with other calves, juveniles, and sub-adults. For bottlenose dolphin calves, sociality is related to maternal behaviors. Unfortunately, much less is known about the development of sociality and emergence of independence for killer whale calves. The purpose of this study was to examine the developmental changes in social behaviors and solitary activities of a killer whale calf across a 36-month period. Focal follow video recordings of a mother-calf pair housed at SeaWorld San Antonio were collected 2-6 times a day for 5-15 min at 6-month intervals. Using a sample of randomly selected video recordings at each month, developmental changes in swims and social interactions with her mother, swims and social interactions with non-maternal partners, and solitary activities (e.g., solitary swims, solitary play) were observed across the months. The calf spent most of her time swimming with the mother across the 36-month period. The time the calf socialized with her mother was greater than the time she socialized with others at each month. Besides her mother, the calf socialized more often with the other adult female compared to adult males. As the calf matured, the increase in the time she spent socializing with adult killer whales other than the mother corresponded with an increase in the rate and time spent in solitary play. The developmental trends of sociality and emerging independence replicate research conducted with calves of other dolphin species. Zoo Biol. 36:11-20, 2017. © 2016 Wiley Periodicals, Inc.

Stable isotope ratios of carbon, nitrogen and oxygen in killer whales (Orcinus orca) stranded on the coast of Hokkaido, Japan.

We analyzed δ(13)C, δ(15)N and δ(18)O in the muscle and liver from killer whales stranded on the coast of Japan. The δ(15)N values in the muscle samples from calves were apparently higher than those in their lactating mothers, suggesting that nursing may result in the higher δ(15)N values in the muscle samples of calves. The δ(15)N value in the muscle samples of male and female whales, except for the calves, were positively correlated with the δ(13)C values and body length, suggesting that the increases in δ(15)N were due to the growth of the whales and increase in their trophic level. In contrast, the δ(18)O values in the muscle samples of female whales except for the calves were negatively correlated with the δ(13)C and δ(15)N values. The δ(18)O may be lower in whales occupying higher trophic positions (δ(15)N), although it might also be affected by geographic and climatic conditions.

Random Leslie matrices in population dynamics.

We generalize the concept of the population growth rate when a Leslie matrix has random elements (correlated or not), i.e., characterizing the disorder in the vital parameters. In general, we present a perturbative formalism to deal with linear non-negative random matrix difference equations, then the non-trivial effective eigenvalue of which defines the long-time asymptotic dynamics of the mean-value population vector state is presented as the effective growth rate. This effective eigenvalue is calculated from the smallest positive root of a secular polynomial. Analytical (exact and perturbative calculations) results are presented for several models of disorder. In particular, a 3 × 3 numerical example is applied to study the effective growth rate characterizing the long-time dynamics of a biological population model. The present analysis is a perturbative method for finding the effective growth rate in cases when the vital parameters may have negative covariances across populations.