Adverse Effects of Ball-Chain Radio-Collars on Female Mantled Howlers (Alouatta palliata) in Panama

The placement of radio- and GPS-collars on primates has advanced the fields of primate behavior and ecology and yielded considerable conservation gains. However, to ensure that the placement of tracking collars remains a humane practice, the reporting of both positive and negative outcomes is required. Here, we evaluate the impacts of radio-collars on the reproduction, behavior, and health of female mantled howlers ( Alouatta palliata ) on Barro Colorado Island, Panama. In June 2005, as part of a behavioral study, we fitted 16 female howlers with ball-chain radio-collars weighing 1.2% of the mean adult female weight. We monitored these 16 collared females and 64 noncollared females across an annual cycle, and recaptured the collared females in July 2006 for collar removal. The mortality rate for collared females across the study year was 6.3% (N=1), while the net loss of noncollared females from study groups was 15.6% (N=10). All collared females reproduced. The behaviors of collared and noncollared females were not significantly different. However, on recapture to remove all remaining collars ( N = 13), 38% of recaptured collared females presented with damage to the dermal layer on the back of the neck and 31% presented with more severe damage extending into the subcutaneous tissue and muscle. Given this physical damage, which was not apparent through binoculars, we cannot recommend using ball-chain radio-collars on female mantled howlers without careful welfare monitoring.