Mortality of radio‐tracked wild rats in relation to transmitter weight and resilience of transmitters in relation to their design

Abstract

We assessed mortality of rats in relation to transmitter weight and tested several types of rat transmitters in order to provide recommendations for their design. We used 21 collars with radio-or dummy transmitters, made of either epoxy or dental acrylic, with external or internal (inside the collar) antennae, on 20 rats (Rattus rattus and R. exulans) in rainforests of New Caledonia. We found that rats chewed and destroyed most external whip antennae and transmitters made of epoxy. Rats, especially males during the reproductive season, with transmitters that weighed 4.7-7.1% of their body weight, had a higher mortality than those with transmitters that weighed 2.1-4.0% of their body weight. We recommend keeping transmitter weight down to about 4% of body weight, constructing transmitters exclusively of dental acrylic and using internal antennae if their heavier weight and lower range do not cause problems for the study.

Causes of mortality in North American populations of large and medium-sized mammals

“…However, several studies in mammals as well as birds, have shown slight increases in predation mortality in radio tagged animals compared with noncollared animals, or animals with implanted transmitters. (Wolton & Trowbridge, 1985;Marks & Marks, 1987;Theuerkauf, Rouys & Chatreau, 2007). This effect was seen primarily with particularly large radio tags fitted on smaller species, which there were few of in our dataset.…”

Necklace-style radio-transmitters are associated with changes in display vocalizations of male greater sage-grouse

“…The distinction between attending and displaying is important, but it is costly and difficult to measure differences in attendance and behaviors between collared and non-collared birds effectively, as it requires intensive monitoring efforts to compare birds marked with color bands only versus those birds with radio-transmitters or among birds outfitted with alternative harness designs. In the later case, it would be ideal to use identical transmitters -we note that the transmitters used in Nevada were 30% heavier than those used in Idaho, although still well under the recommended guidelines of 4% body weight (Theuerkauf et al 2007) for a  2 kg adult male greater sage-grouse.…”

“…One fundamental assumption of telemetry is that radio‐transmitters do not influence behavior or demographics of marked individuals (Millspaugh et al 2012). It is important to test this assumption, as a number of studies on various taxa have documented negative effects of transmitters on survival (Theuerkauf et al 2007, Venturato et al 2009, Fabian et al 2015), but other studies have documented no difference in survival between individuals wearing radio‐transmitters and those without transmitters (Hagen et al 2006). However, comparatively few studies have evaluated whether transmitters cause behavioral changes.…”

Are All Conservation Measures for Endangered Species Legitimate? Lines of Thinking With the European Hamster

“…Nowadays, survival after surgery is now much better and can reach 100% after implantation of transmitters for hamsters (Capber, 2011). Furthermore, some of the transmitters in Koehler et al exceeded 10% of the mass of animals while it is now recommended not to exceed 3-5% (Macdonald and Amlaner, 1980;Theuerkauf et al, 2007). In France, European hamsters are only implanted when their body mass exceeds 150 g. The transmitter weighing 6.5 g does not therefore exceed 4.3% of the body mass of the hamster and, thus, never exceeds the recommended range.…”

“…The use of external transmitters is also possible and does not require surgery, but it can have adverse effects on animals, like handicap (especially collars for hamsters, since they have cheek pouches), perturbation of its behavior, or survival impairment (Webster and Brooks, 1980;Theuerkauf et al, 2007;Kletty et al, 2019). Thus, if internal transmitters can be used, it seems to be a more suitable option.…”