A field-based estimation of eagle predation and scavenging on reindeer calves : towards mitigating human-wildlife conflicts

Abstract: Eagle predation on semi-domesticated reindeer (Rangifer tarandus) calves, both golden (Aquila chrysaetos) and white-tailed eagle (Haliaeetus albicilla) is a well-known issue in Sweden. However, there is a knowledge gap regarding the balance between scavenging and hunting and the role that each of the eagle species has in this issue. This project was set up to fill the knowledge gaps of eagle abundance before, during, and after reindeer calving and the testing of two potential deterrents to repel eagles from reindeer calving areas. During the study period, we made 12, 47, and 17 eagle observations before, during, and after calving respectively. Of these observations, 34 were of GE, 33 of WTE, and for 9 observations the species could not be confirmed. Observations increased during calving and decreased again after calving. No direct attacks on calves have been observed. Two dead calves have been found, but the cause of death could not be allocated to any eagle species. The efficiency of 20 wind ventilators and 17 pyramid prisms was tested for deterring eagles from specific areas. The majority of eagle observations were made in the respective control area, with GLMMs showing significantly higher odds of observing an eagle in the control area compared to the ventilator area. Comparison between control and prism area showed no significant effect, but overlap between the two areas was small. No difference between the two treatments was found. A conclusion on the effect of deterrents can however not yet be made since the study needs more replication.