AMoveE 2014: Roger Powell
Channel: Movebank
Date: 23/05/2014

This talk was presented by Roger Powell on 6 May 2014 as part of the Symposium on Animal Movement and the Environment, held at the North Carolina Museum of Natural Sciences in Raleigh.

Powell RA, 2014, "Dynamic black bears"

Abstract: Female black bears (Ursus americanus) studied in the Southern Appalachians in 1981--2002 did not always move as predicted. During their active period from May to November, female bears should move predominantly to forage. Foraging effort for adult females in the fall was predicted to vary inversely with the annual productivity of hard mast. This makes sense: bears travel only as far as needed to find sufficient food. Contrary to predictions, foraging effort of females varied positively with annual production of squaw root (Conopholis americana), an important food in early summer. Female bears did not respond to the large variation in the summer berry crops. My coworkers and I suggested 2 hypotheses for the responses of adult, female bears to variation in the annual productivity of squaw root: 1) Female bears use extra food in early summer to fuel movements during the breeding season, and 2) Female bears behave as do tits (Parus sp.), whose optimal behavior is to forage at low effort on winter mornings (for bears, in the spring) when food is scarce but to hoard food energetically (for bears, put on fat) when food is abundant. A dynamic model for optimal foraging behavior for bears agreed with field results that foraging effort should vary inversely with the fall mast crop. The model predicted a positive relationship between foraging effort and squaw root production only when bears have a negative energy budget for low squaw root production and a positive energy budget when squaw root production is high. If squaw root production always leads to a negative energy budget, bears should always minimize effort. If production always leads to a positive energy budget, no matter how small, bears should always forage energetically. Actual range of production of squaw root appears to span the energy budget threshold for female bears.