Behavioral correlates of heart rates of free-living Greater White-fronted Geese

We simultaneously monitored the heart rats and behavior of nine free-living Greater White-fronted Geese (Anser albifrons) on their wintering grounds i n northern California. Heart rates of wild geese were monitored via abdomin ally-implanted radio transmitters with electrodes that received electrical impulses of the heart and emitted a radio signal with each ventricular cont raction. Post-operative birds appeared to behave normally, readily rejoinin g flocks and flying up to 15 km daily from night-time roost sites to feed i n surrounding agricultural fields. Heart rates varied significantly among i ndividuals and among behaviors, and ranged from less than 100 beats per min ute (BPM) during resting, to over 400 BPM during night. Heart rates varied from 80 to 140 BPM during non-strenuous activities such as walking, feeding , and maintenance activities to about 180 BPM when birds became alert, and over 400 BPM when birds were startled, even if they did not take night, Pos tflight heart rate recovery Lime averaged < 10 sec. During agonistic encoun ters, heart rate exceeded 400 BPM: heart rates during social interactions w ere not predictable sold from postures, as heart rates were contest-depende nt, and were highest in initial encounters among individuals. Instantaneous measures of physiological parameters, such as heart rate, are often better indicators of the degree of response to external stimuli than visual obser vations and san be used to improve estimates of energy expenditure based so lely on activity data.