Jason N. Waite

Environmental and biological factors influencing maternal attendance patterns of Steller sea lions (Eumetopias jubatus) in Russia

Abstract Maternal attendance patterns in free-ranging wildlife can provide insight into basic biology, foraging behavior, and population dynamics. We collected detailed visual observations of attendance patterns by adult lactating Steller sea lions (Eumetopias jubatus) from 2005 to 2007 on 6 major rookeries in the Russian Far East, including those with an increasing population trend (Sea of Okhotsk), severely depleted populations that were recovering (Kuril Islands), or those that were stable (Commander Islands). Individually identifiable females were observed during the postpartum period, with special attention paid to presence and absence during the day and to departure and arrival times. Within Russia females on several Kuril Islands rookeries exhibited extremely short foraging trip durations (median 6.5–8.0 h) and spent higher proportions of time on the rookery (75–82%), whereas females in the Sea of Okhotsk population had the longest trips (median 19.8 h) and spent the least amount of time on the rookery (60%). Most indices of attendance pattern were more favorable (longer peripartum period, higher proportion of time spent on rookery, shorter trips, and longer visits) than those reported in Alaska and much more so than those in California during El Niño years, where the proportion of time spent on the rookery was nearly half that in Russia. Females >6 years of age had shorter trips and longer visit durations than the youngest females (4–5 years), and older mothers exhibited significantly longer periods of nursing before taking their 1st trip, suggesting greater physical condition for older females. Although trip durations remained constant throughout the season, visit durations shortened significantly as the pups aged, suggesting that increasing nutritional demands of pups are met by more frequent, rather than longer, trips. No apparent relationships between attendance patterns and population status were observed; however, many of the differences in attendance patterns throughout the range of the Steller sea lion could be related to local variation in bathymetry and diet patterns.

Inter- and intra-researcher variation in measurement of morphometrics on Steller sea lions (Eumetopias jubatus)

Substantial effort has been made to increase the accuracy of photogrammetric measurement techniques, especially on marine mammals. However, accuracy of the physical measurements is rarely considered when calculating the photogrammetric accuracy. We examined inter- and intra-researcher variation in the measurement of physical morphometrics of Steller sea lions (Eumetopias jubatus) to assess their potential effects on photogrammetric accuracy and body mass predictions based on photogrammetrically derived morphometrics. Significant differences were found inter-researcher in median standard length and axillary girth and intra-researcher when measuring axillary girth of the same animals. Photogrammetrically derived estimates of these parameters are comparable to physical measurements when taking into account the inherent inter- and intra-researcher variation.

Differentiating between Steller sea lion (Eumetopias jubatus) and northern fur seal (Callorhinus ursinus) scats through analysis of faecal DNA

We describe a method to determine the species of pinniped from faeces collected from sympatric Steller sea lion (Eumetopias jubatus) and northern fur seal (Callorhinus ursinus) rookeries using newly developed species‐specific primers that amplify a 667–669‐base pair segment from the mitochondrial DNA (mtDNA) cytochrome B (cytB) gene region. The primers yielded the correct species in 100% of tissue samples from 10 known animals and 100% of faecal samples from 13 known animals. Species could be identified unequivocally for 87.7% of faecal samples from 122 unknown individuals. The ability to differentiate between scats of sympatrically breeding Steller sea lions and northern fur seals will contribute to the range‐wide knowledge of the foraging strategies of both species as well as allow researchers to examine the niche partitioning and potential resource competition between the two predators.