Correlates of birth origin effects on the development of stereotypic behaviour in striped mice, Rhabdomys

Abstract

The behaviour and physiology of wild animals born in zoos, laboratories and breeding centres can differ substantially from that of their wild-caught (WC) conspecifics. For instance, captive-born (CB) animals are typically more prone to developing abnormal repetitive behaviours. In captive striped mice, Rhabdomys, we first confirmed that birth origin predicted the emergence of stereotypic behaviour (SB), with CB mice being most at risk. Second, to investigate correlates of this birth origin effect, we tested WC and CB striped mice in behavioural tasks to quantify fear/anxiety, activity and perseveration, and measured faecal corticosterone to assess physiological stress. WC mice proved more fearful and less active than CB animals, and had higher levels of faecal corticosterone metabolites. These effects, however, were unrelated to SB. WC mice were also less perseverative and more behaviourally flexible than CB animals, traits that covary with SB. Third, a retrospective analysis of laboratory records showed that SB incidence was significantly lower in adult-caught than juvenile-caught striped mice, with juvenile males being the most severely affected by early removal from the wild. In conclusion, our results indicate that adult, but not juvenile WC striped mice are typically protected against SB development in captivity, despite having poorer welfare than their CB conspecifics. They also reveal profound behavioural changes in CB mice, changes suggestive of altered forebrain function, a hypothesis now needing direct testing. Ó

Early environmental enrichment protects captive-born striped mice against the later development of stereotypic behaviour

“…wild-caught [WC] individuals; Mason, 2006). This effect of birth origin on SB development is evident in the behaviour of captive striped mice, Rhabdomys (Jones et al, 2011): striped mice which spend a prolonged period of time in the wild before capture are substantially less likely to stereotype than CB individuals. Their low SB is linked to increased behavioural flexibility under test compared to that of CB animals, indicating that nonstereotypic WC mice have relatively normal behavioural control.…”

“…The WC founder stock, which originated from a Highveld grassland locality (Gauteng, South Africa; 27 • 55 S, 26 • 4 E), were trapped for use in other behavioural studies (see Jones et al, 2011).…”

“…Their low SB is linked to increased behavioural flexibility under test compared to that of CB animals, indicating that nonstereotypic WC mice have relatively normal behavioural control. However, as a group, regardless of whether or not they are stereotypic, WC mice are more fearful than CB individuals, have higher corticosteroid outputs, and are concerningly far more inactive (Jones et al, 2011).…”

“…Retrospective analysis of historical data sets (e.g. Jones et al, 2011), which avoids these issues, provides some insights into the correlates of birth origin effects, but the results from such analyses do not necessarily provide causal insights and are limited by the variables recorded. Furthermore, catching new animals from the wild precludes the investigation of some research questions principally because the experiences of WC animals before capture are unknown and cannot easily be manipulated, making it difficult or impossible to tease apart the relative contributions of early social environment, physical environment, and/or prior lack of exposure to humans on their subsequent responses to captivity.…”

“…Because little is known about how cage characteristics influence the form of SB (Würbel, 2006), and because WC mice that stereotype exclusively circuit run, we also recorded preferred SB form both before and after transfer to standard caging. Finally, given that non-stereotypic WC striped mice are very inactive, and that stereotypic WC striped mice have markedly time-consuming SBs (Jones et al, 2011; responses suggestive of fear and frustration respectively), during Phase 2 we additionally recorded the proportion of time that striped mice spent engaged in nonstereotypic activity in the home cage, or performing SB in the nest.…”