Search

Although the advent of high‐resolution GPS tracking technology has helped increase our understanding of individual and multispecies behavior in wildlife systems, detecting and recording direct interactions between free‐ranging animals remains difficult. In 2023, we deployed GPS collars equipped with proximity sensors (GPS proximity collars) on brown bears (Ursus arctos) and moose (Alces alces) as part of a multispecies interaction study in central Sweden. On 6 June, 2023, a collar on an adult female moose and a collar on an adult male bear triggered each other's UHF signal and started collecting fine‐scale GPS positioning data. The moose collar collected positions every 2 min for 89 min, and the bear collar collected positions every 1 min for 41 min. On 8 June, field personnel visited the site and found a female neonate moose carcass with clear indications of bear bite marks on the head and neck. During the predation event, the bear remained at the carcass while the moose moved back and forth, moving toward the carcass site about five times. The moose was observed via drone with two calves on 24 May and with only one remaining calf on 9 June. This case study describes, to the best of our knowledge, the first instance of a predation event between two free ranging, wild species recorded by GPS proximity collars. Both collars successfully triggered and switched to finer‐scaled GPS fix rates when the individuals were in close proximity, producing detailed movement data for both predator and prey during and after a predation event. We suggest that, combined with standard field methodology, GPS proximity collars placed on free‐ranging animals offer the ability for researchers to observe direct interactions between multiple individuals and species in the wild without the need for direct visual observation. [ABSTRACT FROM AUTHOR]

Partial migration, whereby a proportion of a population migrates between distinct seasonal ranges, is common throughout the animal kingdom. However, studies linking existing theoretical models of migration probability, with empirical data are lacking. The competitive release hypothesis for partial migration predicts that due to density‐dependent habitat selection, the proportion of migrants increases as the relative quality and size of the seasonal range increases, but decreases with increasing migration cost and population density. To test this prediction, we developed a quantitative framework to predict the proportion of migrants, using empirical data from 545 individually GPS‐marked moose Alces alces from across Fennoscandia, spanning latitudes of 56° to 68°N. Moose contracted their ranges to common and spatially limited winter areas (typically at lower elevation), but expanded them during summer due to an increase in suitable habitat (at highland ranges). As predicted from our model, a better and larger highland range relative to the lowland range corresponded to a higher proportion of migrants in an area. Quantitative predictions coupling the balance of habitat availability of seasonal ranges with the probability of migrating in a large herbivore is a necessary step towards an enhanced understanding of the mechanisms underlying migration at the population level. [ABSTRACT FROM AUTHOR]