Data from: Calculating the ecological impacts of animal-borne instruments on aquatic organisms

1. Animal-borne instruments provide researchers with valuable data to
address important questions on wildlife ecology and conservation. However,
these devices have known impacts on animal behaviour and energetics. Tags
deployed on migrating animals may reduce reproductive output through
increased energy demands or cause phenological mismatches of foraging and
nesting events. For marine organisms, the only tagging guidelines that
exist are based on lift and thrust impacts on birds – concepts that do not
translate well to aquatic animals. Herein, we provide guidelines on
assessing drag from animal-borne instruments and discuss the ecological
impacts on marine organisms. Of particular concern is the effect of drag
from instruments to the welfare of the animals and for the applicability
of collected data to wild populations. 2. To help understand how drag from
electronic tags affects marine animals in the wild, we used marine turtles
as model aquatic organisms and conducted wind tunnel experiments to
measure the fluid drag of various marine turtle body types with and
without commercially available electronic tags (e.g. satellite, TDR, video
cameras). We quantified the drag associated with carrying biotelemetry
devices of varying frontal area and design (squared or tear drop shaped)
and generated contour plots depicting percentage drag increase as a
framework for evaluating tag drag by scientists and wildlife managers.
Then, using concepts of fluid dynamics, we derived a universal equation
estimating drag impacts from instruments across marine taxa. 3. The drag
of the marine turtle casts was measured in wind speeds from 2 to 30 m s−1
(Re 3·0 × 104–1·9 × 106), equivalent to 0·1–1·9 m s−1 in seawater. The
drag coefficient (CD) of the marine turtles ranged from 0·11 to 0·22,
which is typical of other large, air-breathing, marine vertebrates
(0·08–0·26). The CD of tags in reference to the turtle casts was 0·91 ±
0·18 and most tags caused minimal additional drag (<5%) to adult
animals, but the same devices increased the drag for juveniles
significantly (>100%). The sensitivity of aquatic animals to
instrument drag is a dynamic relationship between the fluid flow patterns,
or CD, and the frontal area ratio of the animal and tag. 4. In this paper,
we have outlined methods for quantifying the drag costs from animal-borne
instrumentation considering the instrument retention time (time to release
from the animal) and the activity of the instrumented animal. With this
valuable tool, researchers can quantify the drag costs from animal-borne
instrumentation and choose appropriate tags for their intended study
organism and question. Reducing drag will ultimately reduce the impact on
the instrumented animals and lead to greater biological realism in the
collected data.