At South Georgia, the diet of Wilson's storm petrel was studied using the regurgitates of adults arriving to feed chicks. Feeding frequency and meal size were estimated by weighing chicks twice daily, or in some cases every 3 h during daytime. Crustaceans contributed 98% of the total number of individual items and 68% of the total weight consumed; fish, 1% of the number of items and 28% of the weight. The most abundant crustacean was the amphipod Themisto gaudichaudii, which accounted for 90% of the total number but only 44% of the total weight of crustaceans eaten. Most (79%) of the Themisto were juveniles. Euphausiids were much less numerous in the diet (5% by number) but were the main group by weight (55%); most (52%) were Antarctic krill, with juveniles and sub‐adults (25–50 mm long) predominating. Mysids, copepods and barnacle larvae were also present. Fish were all myctophids (lanternfish), Protomyctophum normani and P. bolini being identified; specimens were 50–85 mm long and weighed 1–4 g. Meal sizes averaged 6‐5‐7‐5 g (14–22% adult body mass); about 75% of chicks were fed each day (mainly at night), about 10% probably receiving meals from both parents. A review of storm petrel diets emphasizes the importance of fish to Oceanodroma species and of crustaceans to Oceanites, Garrodia and Pelagodroma. Euphausiids and amphipods (chiefly Themisto and Hyperia) are the main crustacean prey and range from 5–50 mm and 0‐005‐0‐7 g. Myctophids are the main fish prey and range from 20–100 mm and 1–5 g. Meal size ranges from 15–25% adult body mass and chicks are fed on 50–85% of days. This low delivery rate is mainly responsible for the disproportionately slow growth and long fledging period of storm petrel chicks.
Aggression in male gray seals has been extensively studied; however it is often simplistically assumed that threat signals are mainly cephalic in nature for this species. We report on an undescribed and apparently new kind of threat signal used by male gray seals we term a Body Slap. The behavior has been observed at breeding sites in eastern England since 1993 but has not been studied ethologically or reported elsewhere. The aims of this study were to describe the behavior, test the influence of topographic variation on its frequency of occurrence, examine if it is used to signal dominance or submission, and to place it in intra‐ and interspecific contexts. Our results show Body Slaps were performed in 66.3% of interactions and by 57.2% of males; it was not performed by females. The Body Slap was positively associated with the Approach and Open‐Mouth Threat behaviors but was not related to dominance; nevertheless, display rates were greater for subsequent winners. These findings suggest that the Body Slap carries information about male resource holding potential and does not signal submission. This study furthers our understanding of geographic variants of male threat behaviors and of pinniped nonvocal communication.
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