Do researchers impact their study populations? Assessing the effect of field procedures in a long term population monitoring of sea kraits

Abstract

Long term population monitoring is essential to ecological studies; however, field procedures may disturb individuals. Assessing this topic is important in worldwide declining taxa such as reptiles. Previous studies focussed on animal welfare issues and examined short-term effects (e.g. increase of stress hormones due to handling). Long-term effects with possible consequences at the population level remain poorly investigated. In the present study, we evaluated the effects of widely used field procedures (e.g. handling, marking, forced régurgitation) both on short-term (hormonal stress response) and on long-term (changes in body condition, survival) scales in two intensively monitored populations of sea kraits (Laticauda spp.) in New Caledonia. Focusing on the most intensively monitored sites, from 2002 to 2012, we gathered approximately 11200 captures/recaptures on 4500 individuals. Each snake was individually marked (scale clipping -I-branding) and subjected to various measurements (e.g. body size, head morphology, palpation). In addition, a subsample of more than 500 snakes was forced to regurgitate their prey for dietary analyses. Handling caused a significant stress hormonal response, however we found no detrimental long-term effect on body condition. Forced régurgitation did not cause any significant effect on both body condition one year later and survival. These results suggest that the strong short-term stress provoked by field procedures did not translate into negative effects on the population. Although similar analyses are required to test the validity of our conclusions in other species, our results suggest distinguishing welfare and population issues to evaluate the potential impact of population surveys.

Shelter availability, stress level, and digestive performances in the aspic viper

“…We obtained 100-500μl of blood per snake via intracardiac punctures (<5% of total body mass, using 30G needles). This technique is routinely employed in snakes (Bonnet et al, 1994;Bonnet et al, 2001;Fauvel et al, 2012). The blood was immediately centrifuged (3min at 10,000g), and the plasma was separated and stored at −25°C until assay.…”

Differential uses of coral reef habitats by a poorly‐known cryptic fish predator

“…In this study, an innovative and more efficient technique was used; G. chilospilus were collected from their main predators, the sea snakes Laticauda laticaudata and Laticauda saintgironsi , via gentle forced regurgitation (Brischoux et al ., ). These sea snakes consume almost exclusively anguilliform fishes and because the prey are non‐spiny, the snakes readily regurgitate them (Brischoux & Bonnet, ) without any effect on their own survival (Fauvel et al ., ). Sea kraits clearly represent excellent natural samplers and this unusual method has been successfully used in previous studies (Briand et al ., , ; Ineich et al ., ; Reed et al ., ).…”

“…(), who demonstrate their underestimated and unexpected diversity and abundance. This statement was supported by subsequent studies (Bonnet, ; Bonnet et al ., ; Briand et al ., ; Brischoux et al ., , ; Fauvel et al ., ). One such study assessed, for example, the role played by these carnivorous fishes in coral‐reef trophic networks (Briand et al ., ).…”

A frontier in the use of camera traps: surveying terrestrial squamate assemblages

“…In addition, during capture and handling, although stress may negligibly affect long‐term survival of some species (Langkilde and Shine ; Fauvel et al. ; Holding et al. ), other species are clearly affected (Martin and Avery ; Bateman and Fleming ; Scroggie and Clemann ).…”