External transmitter attachment in snakes: a systematic review of methods, efficacy, and impacts

Abstract

Background The advent of telemetry has revolutionized wildlife research in recent decades. For telemetry to be effective, transmitting devices must remain attached to study animals throughout a period of interest and without impacting pertinent behaviors. Surgical implantation remains the most common method used to attach transmitters to snakes, but concerns about the effects of transmitter implantation on snake health and behavior have motivated many researchers to opt for external transmitter attachments. Despite the increasing use and diversification of external transmitter attachment techniques in snake research, to date there have been no comprehensive reviews examining the methods, efficacies, and adverse impacts reported in the literature. We therefore conducted a systematic review of past research involving external attachment of transmitters on wild snakes. We extracted data from relevant studies to determine whether and how snake traits and transmitter attachment details correlated with efficacy and likelihood of adverse effects. Results The 54 cases that met inclusion criteria covered 33 species and 3 families. External attachment was biased toward smaller-bodied snakes (median = 186 g), although larger snakes had longer retention durations. Adverse impacts were reported in 37% of studies (n = 20), and included altered behavior and movement, skin wounds at the attachment site, and death. Smaller snakes were more likely to exhibit adverse impacts from attached transmitters. Except for caudal attachments in rattlesnakes, attachment method did not have a significant effect on attachment duration. However, attachment method did influence the probability of causing adverse effects, with glue being the most likely to cause negative impacts. Conclusions Externally attaching transmitters to snakes is an increasingly popular alternative to surgical implantation. To provide guidance to researchers considering this approach, we conclude our systematic review with recommendations for attaching external transmitters to snakes. Actions such as minimizing transmitter weight and protrusion, using shorter and stiffer antennas, and using flexible adhesives may help to avoid commonly reported problems. We encourage more consistency in reporting methodological details and results pertaining to efficacy and animal welfare.