Animal lifestyle affects acceptable mass limits for attached tags

Abstract

Animal-attached devices have transformed our understanding of vertebrate ecology. To minimize any associated harm, researchers have long advocated that tag masses should not exceed 3% of carrier body mass. However, this ignores tag forces resulting from animal movement. Using data from collar-attached accelerometers on 10 diverse free-ranging terrestrial species from koalas to cheetahs, we detail a tag-based acceleration method to clarify acceptable tag mass limits. We quantify animal athleticism in terms of fractions of animal movement time devoted to different collar-recorded accelerations and convert those accelerations to forces (acceleration × tag mass) to allow derivation of any defined force limits for specified fractions of any animal's active time. Specifying that tags should exert forces that are less than 3% of the gravitational force exerted on the animal's body for 95% of the time led to corrected tag masses that should constitute between 1.6% and 2.98% of carrier mass, depending on athleticism. Strikingly, in four carnivore species encompassing two orders of magnitude in mass ( ca 2–200 kg), forces exerted by ‘3%' tags were equivalent to 4–19% of carrier body mass during moving, with a maximum of 54% in a hunting cheetah. This fundamentally changes how acceptable tag mass limits should be determined by ethics bodies, irrespective of the force and time limits specified.

The impact of bio-logging on body weight change of the Eurasian beaver

“…However, the relatively slow swimming speed of Eurasian beavers compared to other aquatic or semi-aquatic species may make them less susceptible to negative impacts from tag-induced drag. Indeed, drag is influenced by the speed and acceleration of the tagged animal, with slower moving animals not relying on high acceleration to capture prey being less impacted [ 9 ]. Great cormorants ( Phalacrocorax carbo ) were only negatively affected by drag from a tag at swimming speeds >1.4 m/s [ 4 ].…”

“…Generally speaking, the impact of tag weight is a primary concern, and contemporary guidelines endorse continued miniaturization of tags [ 4 ]. The total weight of a tag should not exceed 0.7–10% of body weight depending on the species and recommendations from different authors [ 5 – 9 ]. Moreover, negative effects from bio-logging can be caused by capture stress [ 8 , 10 ] and vary depending on the attachment method [ 11 ].…”

Guidelines for Telemetry Studies on Snow Leopards

“…Several different heuristics for collar size and weight limits have been employed, e.g., the collar weight should not exceed 2, 3, or 5% of the animals' weight [30,33,34]. Wilson et al [35] showed that when animals moved at a high speed, forces exerted by the collars increased dramatically: a collar weighing 3% of a Cheetah's (Acinonyx jubatus) body weight exerted forces equivalent to 54% of the body weight. Care should be taken to select a collar model as light as possible; for felids that are dependent on agility and speed, collars should probably weigh less than 2% of the animals' body weight.…”

A guide to sampling design for GPS-based studies of animal societies

“…S1). Among these are ethical and practical limitations when capturing and tagging animals, and ongoing research and development is aimed at understanding and minimizing these limitations (Portugal & White 2018;Klegarth et al 2021;Portugal & White 2021;Wilson et al 2021). Here, we assume that researchers follow ethical and legal guidelines for deploying GPS devices and focus on providing guidance on how to design the deployment of GPS devices to optimize data collection for addressing different research questions (Fig.…”

“…Among these are ethical and practical limitations when capturing and tagging animals, and ongoing research and development is aimed at understanding and minimizing these limitations (Portugal & White 2018; Klegarth et al . 2021; Portugal & White 2021; Wilson et al . 2021).…”