Thursday, 11 April 2013

Learning from non-conservation translocations: "Conspecifics can be aliens too..."

I was very glad to receive the paper featured in this post from one of the co-authors, Jocelyn Champagnon, as this review has some important conclusions to draw in terms of restocking practices. The authors have not restricted themselves to looking at restocking for conservation purposes only, instead, they draw on a range of reasons that result in the mixing of conspecifics from wild and captive sources and their conclusions are all the more valuable as a result.  These release events include making a target population of a threatened species viable, enhancing future harvests of for example, game birds, unintentional escapes from fish farms and fur farms and releases motivated by an ethical standpoint on animal welfare.  These and other reasons for release are described in the paper in a useful and enlightening summary that really opened my eyes to the diversity of reasons that can result in conspecifics from captive and wild populations mixing.

The review summarises the effects of restocking (intentionally or not) on wild and translocated individuals using 233 studies to provide a thorough overview of the possible implications. The explanations are too detailed to cover here but include behavioural, genetic, demographic and pathogenic impacts, both positive and negative for both wild and captive-bred individuals. Of particular interest to me were revelations on dispersal behaviour; in mobile species captive-bred individuals tend to disperse further than their wild counterparts. This means that the intended positive effects of restocking e.g. improved social interactions, are not attained and furthermore, the captive-bred animals are more likely to perish during migration, select unsuitable habitat, and fail to breed.  Another interesting finding is that population trends may be positive due to the introduction of new individuals to the group but practitioners should be aware that this might mask underlying problems. Mixing many individuals in one site might result in better demographic and social dynamics but if the reason for decline is unfavourable habitat, eventually the captive-bred animals may also succumb in time.

As part of the conservation translocation community, I think we would benefit by wider adoption of the following recommendations adapted from the paper:
  • Avoid selection in captivity.
  • Choose genetic strains that are as close as possible to wild target populations
  • Vaccination and diseas screening should be routine practice.
  • There is an urgent need for monitoring the size, duration and success of restocking events and this would be enhanced if individuals were identifiable using e.g. tags or rings etc.
  • Policy-makers and managers need to encourage studies that reduce research bias e.g. addressing the lack of rigorous studies on harvest enhancing interventions.
  • Practitioners in conservation, game management, fisheries, epidemiology and other relevant fields would benefit by working across disciplines.
By using restocking events from a range of motivations and circumstances, Jocelyn and her co-authors have added weight to the idea that translocations for non-conservation purposes have much to teach us when using translocations to effect conservation benefit. Ultimately, mixing wild and captive-bred individuals will impact upon each other regardless of how well-intentioned the motivation, if it is intentional at all. Augmenting wild populations have many positive and negative impacts but it is critical to realise that most of the effects covered here are unintended and unforeseen. The process of removing individuals from the wild has the effect of altering traits, or at least, their offspring's traits, resulting in a markedly different animal. Many of these problems are familiar from invasive species biology but with the added problem that genetic and behavioural barriers that normally occur between wild animals and non-native invasives are not there. As the title of the paper neatly states, conspecifics can be aliens too and this comes with all the associated problems of invasive non-natives and more.

For the full paper (and I'd recommend that you read the full thing) please contact Jocelyn by email or download using the following citation:

Champagnon, J., Elmberg, J., Guillemain, M., Gauthier-Clerc, M., & Lebreton, J.-D. (2012). Conspecifics can be aliens too: A review of effects of restocking practices in vertebrates. Journal for Nature Conservation, 20(4), 231–241. doi:10.1016/j.jnc.2012.02.002

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