Knowing size‐at‐age is important for determining food requirements and making inferences about the nutritional status of individuals and their populations. Accurate growth curves are also needed to quantify drug dosages to treat wounded or entangled animals. However, body sizes are often based on small numbers of measured animals that must be improved as new data become available. We updated an existing body growth model for N...

This paper describes the relationship between eastern North Pacific gray whale calf production and environmental conditions in the Pacific Arctic where they feed. The results show how interannual variation in sea ice cover in the Bering and Chukchi Seas along with broader indices of North Pacific climate, such as Pacific Decadal Oscillation (PDO) and North Pacific Index (NPI), are linked to variation in gray whale reproductive...

Unoccupied aerial systems (UAS) have become common tools for ecological monitoring and management. However, UAS use has the potential to negatively affect wildlife. Both policy makers and practitioners require data about the potential impacts of UAS on natural biota, but few studies exist and some of the published results conflict. We conducted two experiments to assess the responses of chinstrap penguins ( Pygoscelis antarcti...

Estimating the number of dolphins in a group is a challenging task. To assess the accuracy and precision of dolphin group size estimates, observer estimates were compared to counts from large‐format vertical aerial photographs. During 11 research cruises, a total of 2,435 size estimates of 434 groups were made by 59 observers. Observer estimates were modeled as a function of the photo count in a hierarchical Bayesian framework...

Four geographic forms of spinner dolphin ( Stenella longirostris ) occur in the eastern tropical Pacific. Two of the forms are pelagic: the eastern and whitebelly, and two are coastal: the Central American and Tres Marias spinner dolphins. Of these, only the Tres Marias form lacks recognition appropriate for developing management and conservation plans. Vertical aerial photographs of 57 spinner dolphin schools taken between 19...

Reproductive parameters were estimated and compared for eastern North Pacific populations of common dolphins using specimen and photogrammetric data. Age and length data for Delphinus capensis and D. delphis specimens recovered as bycatch or strandings were used to estimate the postnatal growth rates needed to estimate age for calves measured in aerial photographs. Bayesian methods propagated uncertainty among models and revea...

Molecular assays were used to determine the sex of 1,294 biopsied common dolphins (658 long‐beaked common dolphins, Delphinus capensis , and 636 short‐beaked common dolphins, D. delphis ) in the Southern California Bight. Sex ratio differed substantially between the two species; females comprised 241 (36.6%) of D. capensis samples and 410 (64.5%) of D. delphis samples. All biopsies were taken either from a large research ship...

A bstract We conducted shore‐based sighting surveys to estimate the number of northbound migrating gray whale calves passing Piedras Blancas, California, for seven consecutive years (1994–2000). In addition, we conducted aerial surveys to determine offshore distribution of the migration in 1994 and 1995, measured day/night migration rates with thermal sensors in 1994–1996, and maintained concurrent replicate watches near the p...

A bstract Estimates of Steller sea lion ( Eumetopias jubatus ) pup production are valuable for estimating population trend and size. Currently in Alaska, pups are counted by visiting rookeries, driving older animals into the water, then walking through the rookeries and counting the pups, a highly disruptive procedure. At smaller rookeries, with good vantage points, pups are occasionally counted from the periphery of rookeries...

A bstract We recorded the blows of gray whales during their southbound migration past central California in January 1994, 1995, and 1996, using thermal imaging sensors. For our sampling purposes, we defined day (0730–1630) and night (1630–0730) to coincide with the on/off effort periods of the visual counts being conducted concurrently. We pooled data across the three years of sampling and tested for diel variation in surfacin...

A bstract Analyses of skeletal and external morphology of spinner dolphins killed in to the yellowfin tuna purse‐seine fishery in the eastern tropical Pacific led to the description of two subspecies of spinners from this region, the eastern spinnen dolphin and the Central American spinner dolphin (Perrin 1990). However, when we examined lengths of spinner dolphins taken from vertical aerial photographs from the same area, we...