Out of the frying pan and into the fire? Translocation spells trouble for social species

Translocation - taking animals from one place and moving them to another - is becoming an increasingly common practice both in conservation and as a mitigation measure for development projects. However, a recent study¹ has shone a spotlight on the questionable success rates and lack of monitoring associated with mitigation-driven translocations. Finding a replacement habitat might seem simple enough, but there are many more factors related to a species' well-being that may make survival at these new sites a considerable challenge.

Mitigation-driven translocations aim to "reduce animal mortality caused by human activities (e.g development), by relocating individuals away from project sites" (Germano, J. M. et al, 2015)

They differ from conservation-driven translocations, which aim to augment or re-establish populations in areas where they are in decline or have been wiped-out¹. Similar kinds of translocations are expected to rise in response to climate change, moving species beyond their historical range, for example to higher elevations, in order to mitigate species extinctions due to rapid changes in environmental conditions². This is also known as ‘assisted migration' - something I've discussed on this blog before.

Many countries have strict regulations regarding the relocation of protected species. In the UK, for example, great-crested newts are highly protected, and mitigating development related impacts on them can cost up to £100,000-£200,000 per project¹. So if we're spending this much money on it, we'd better be sure we're doing it right.

The problem Germano et al. (2015) highlight, is that such mitigation-translocations are often "inappropriately executed, poorly documented, and unquestioningly used without regard to larger, more strategic conservation goals." In these circumstances, the word ‘mitigation' seems simply to mean balancing out negative impacts of a development project by performing a positive action elsewhere. This, however, is just one small portion of what mitigation should be. As described in the paper, the Business and Biodiversity Offsets Programme advocates a "mitigation hierarchy", which involves four key steps: avoid, mitigate, restore or rehabilitate and offset.

Sadly, many mitigation translocations fail to follow best scientific practice. Without monitoring, we cannot say for sure whether the translocated animals survive to establish or enhance a viable population at the release site. The numbers moved may not have represented a substantial enough proportion of the source population or, if too many are moved, the population at the release site may exceed the ecological carrying capacity, leading to mortalities among the resident population. There is also the risk of disease transmission and social disruption (Aiello et al. 2014, in Germano et al. 2015).

As an example, Germano et al. highlight an interesting study into the social disruption that translocations can cause and how this affects survival rates...

Keep your friends close, and your enemies closer - The case of the Kangaroo rat.

For social species, translocations are particularly tricky. Stephens' Kangaroo rats, like many other animals, form social relationships with their close neighbours. They get to know who's who, where one rat's territory ends and another begins, where potential mates are, and who's likely to beat them in a fight. Once these neighbourly relationships are established, it saves a lot of time, energy and unnecessary aggression in day-to-day interactions. This is due to a phenomenon known as the "dear enemy" effect, whereby territorial animals tend to respond less aggressively towards their neighbours, than they do toward unfamiliar animals.

It makes sense, therefore, that if you move them to an entirely new area, with a whole population of unfamiliar Stephens' Kangaroo rats, it takes a lot of time, energy, and risk of injury to adapt to these new social conditions. And that leaves less time and energy available to search for food or potential mates.

In their study Shier and Swaisgood spent a lot of time observing and marking their population of kangaroo rats to figure out who each rat's neighbours were (neighbour meaning they had no other rat with a territory between them). They then assigned animals to one of two treatment groups - those to be translocated with their neighbours, and those to be translocated without.

Their results showed that a significantly greater number of the kangaroo rats translocated with their neighbours survived and reproduced than those translocated without neighbours. More than twice as many of the surviving females reproduced, resulting in twenty-four offspring being produced in the with-neighbour group for every one produced in the without-neighbours group.

They also observed the behaviour of the animals immediately after release and found that those translocated with neighbours started fewer fights, spent more time foraging and established a greater number of burrows.

These findings indicate that maintaining neighbour groups during translocation of Stephens' kangaroo rats has a positive effect on their settlement, survival and reproductive success. And it could well be the case that this applies to other social animals, particularly those that, like the Stephens' kangaroo rat, are solitary, aggressive territorial species.

This highlights the importance of knowing not just what's a good habitat to move your species to, but understanding how that species lives and interacts with the animals around it.

"Tit for tat" ain't all that

Failure to address these sorts of factors raises questions as to whether such attempts to save animals wildlife from development sites by moving them out of the way are simply a more socially acceptable way of them perishing - out of sight, rather than under a bulldozer.

"[T]he relative success of scientific conservation-driven translocations is being used to justify the use of mitigation-driven translocations globally."¹. But if the latter are not being designed with the same level of scientific rigour, such justification cannot be warranted. We therefore need to "move from "tit-for-tat" translocations to a more strategic allocation of resources in order to mediate impacts at development sites". And it should be the responsibility of developers, consultants and regulatory agencies to validate the use of translocation by demonstrating its effectiveness in achieving the desired conservation outcomes. We must be confident we can ensure the survival of the population at the release site - not just their successful removal from the development site.

If projects were to carry out greater monitoring of populations post-release we could learn a huge amount about the impacts and effectiveness of different translocations. Each translocation should be seen as an opportunity to test hypotheses, allowing us, over time, to vastly improve future practice¹.

References:

1. Germano, J. M. et al. Mitigation-driven translocations : are we moving wildlife in the right direction ? Frontiers in Ecology and the Environment (2015) [Available online preprint: http://www.esajournals.org/doi/abs/10.1890/140137 Accessed 29 Jan 2015]
2. Shier D. M. and Swaisgood R. R. Fitness costs of neighborhood disruption in translocations of a solitary mammal. Conservation Biology 26 116-23 (2012)

Photo credits:

Great crested newt tadpole by Karen Blakeman on Flickr.
Stephens' kangaroo rat - © Mark Chappell