A discussion started when a link was posted to a website article in 2015, in which the relocation (or translocation) of snakes from an urban or in another way human inhabited area to another, human-free location. I cite: "Translocation (releasing a rescued animal in a new location and/or habitat different from where it was picked up) has adverse consequences on both ecosystems (location of rescue in cities; and location of release into forests)."
The article continues, sketching the effect:
"Effects on humans:
The rescue site will see an exponential spike in rodent population as a natural consequence of eliminating the predator. This intensifies the spread of disease by the increasing rodent population who quickly destroy our stored grain and crop cycles and put a direct strain on our food source. The absence of the rescued snake means an increase in the number of rats, this also invites other local snakes who come in to take advantage of this new food source.
Effects on snake:
Away from home range and finding itself in unfamiliar habitat, the snake must start from scratch to establish its sources of food, water, shelter and local knowledge of its predators. This leaves the snake wandering around for months using the trial and error method, thus increasing the potential for human-animal conflicts, now emerging as a vicious cycle. There is also enhanced conflict between the newly released snake and resident snakes of the local habitat, the survival of both are at great risk. A snake from the city could also be a carrier of various diseases.
Effects on ecosystem:
In one move, translocation disrupts the local food chain and natural order of resident species at rescue and release location, thus unbalancing both ecosystems. It is clear that releasing a rescued snake as far away as possible is merely a false safety measure that serves neither the snake nor humans. Whether it stems from a lack of education and awareness or is an indulgence of deep seated fears, rescuers cannot employ sympathetic management in place of common sense. They depend on the understanding and tolerance of everyday citizens to be able to manage urban wildlife in the correct manner."
The article evoked mixed reactions in the Facebook group Snake Handlers of Southern Africa. In this group are, of course, a lot of snake handlers who rescue and relocate snakes on a daily basis. Needless to say, the article was not taken heartily by all snake catchers.
Thea Litschka-Koen, who has a long history of snake rescue and relocation (as is seen in the wonderful BBC documentary about her work 'Black mamba, white witch') reacted in a comment: "Mmmmm interesting. Relocating snakes must be responsibly but i do not see why it would be a death sentence if the habitat is the same. We followed 11 mambas, 6 of which were from 80km away (as the crow flies ), for 9 months. They did not only survive, but thrived. Saying that, when i was still learning, i took three Swazi rock snakes from the highveld to the lowved and they did not do well at all for obvious reasons. There are basically two options when rescuing snakes. 1) find a habitat that is the same and not near humans to give it the best chance possible or 2) destroy it. We have probably rescued and relocated close to 3000 snakes but we always take care when selecting the release sites. Luckily we have an abundance of large natural bush areas to chose from. Until there is scientific evidence to prove otherwise, i will continue to rescue and relocate. What choice do we have?"
One of the members of this group, Etienne Venter, formulated very well the
point of view of no doubt many of these snake handlers: "This
whole discussion is realy pointless, because as Thea said whe don't have a choice
and if you think that we're going to convince most people to live side by side
with snakes in the near future you're living in a dream world."
Others were careful, such as Daniel Louw: "In my view, it depends mainly on the species. "Hunting" snakes, like Black Mambas, have an excellent chance at survival but slow moving, "ambush" snakes, like Puff Adders, might struggle."
Shine and Koenig (2001) defined the controversy
in the following words: "The last few decades have seen the emergence of a
dichotomy in approaches to wildlife management. One stream consists of
scientists trained in ecology and conservation biology, who frame their research
projects in terms of population viability. The other stream involves members of
animal-welfare groups, generally with little scientific training. These groups
focus on the fate of individual animals, and their most common direct
interaction with wildlife involves animal ‘rescue’".
In this discussion we cannot ignore the fact that most snake handlers are not only in it because of their unselfish compassion with the snake or their concern for nature conservation, but without doubt also because they simply like what they do. For some it is probably part of their 'reason for being'. Their activities are part of what makes them what they are in their own eyes and in the eyes of the world. It is their passion.
Time to do some further reading.
Mindy Walker (Walker e.a. 2009) and others did extensive research when
translocating a whole population of Timber rattlesnakes (Crotalus horridus) in
Kansas from a threatened den (the place would be occupied by building
activities) to another, nearby location. Very much care was taken that the new
location would have all necessary characteristics for this species. It's
absolutely worth reading how they did it. Six of the relocated snakes were
followed telemetrically in consecutive two years. The relocation experiment was
considered a succes:
"The relocated snakes ranged, survived, and behaved seasonally in a fashion that mirrors undisturbed populations within 50 km. Based upon behavior and survival of the tracked snakes through the second full activity season after relocation, during which time their foraging loops became less erratic and significantly smaller, we believe this effort has been successful, and that our results provide a more realistic definition of success than others have demanded."
As Shine & Koenig (2001) also pointed out, certain kinds of reptiles are more likely to be rescued than others. Crepuscular species and species active during the night are less likely to be seen by people, some species are less likely to dwell in towns or around houses. It is plausible that species that are most adaptive and more or less take every sort of prey they can get, will be found most often in places where humans live, and that these species – when 'rescued' and relocated, are most able to adapt to their new environment too. Species that actively search and hunt prey, could be more adaptive than species that find a place in an environment and wait for prey. Solitary living species are less dependent of other individuals, of a social context, and would probably be less vulnerable when relocated.
There is a remarkable omission in the studies of Walker (2009): notwithstanding all the research efforts on the
new location, it was not studied with which other predating animals the new
population rattlesnakes were to be competitive. Prey availability was studied,
but not which animals were already present that predated these prey animals. It
was consequently never studied whether other fauna species in the relocation
area suffered in these years or not. The total focus has been on the
rattlesnakes. In the study of Shine & Koenig (2001) there is more attention for
this aspect. For instance, they mention the risk of spreading pathogens from
escaped captive pets into wild populations. Also, they warn for the introduction
of novel genetic material: "such genetic manipulations may also compromise the
genetic distinctiveness of local populations." And last but least, they state
that mostly large predators were translocated, especially snakes. "Like all top
predators, such animals tend to be relatively rare and thus, their translocation
have ecological impacts on both the ‘‘donor’’ and ‘‘recipient’’ areas."
In a healthy environment the ecological 'slots' are already taken by local snakes, and immigrants have to find a place that in fact is already taken. If they share the preference for a certain prey species, there might be not enough for both. If the newcomer is not a specialist but preys on a variety of prey, it is probable that more specialized species are at a disadvantage. For instance: if a relocated mamba kills a lot of frogs because they are relatively abundant in the new area, then a food specialist that preys solely on frogs and toad, possibly loses its stock food and dies, while the mamba after having killed most frogs, simply continues to feed on mice or birds. Overpopulation will eventually have to end with reduction of the population until the old equilibrium is reached. This seems a plausible hypothesis, I think, but one with lots of unsure details, difficult to prove for concrete cases. Mamba's seem to be very strong and adaptive, and it would not be impossible that they survive at the cost of other species. I don't say they do, but it would be possible.
In the light of this considerations, the effects of relocating will differ
from species to species. If relocation is considered, it would be wise to do so
only if the specific needs and habits of the species involved, are known, and a
prediction can be made of the chances for the animal in the new location.
On the other hand, in individual cases the argument of the snake rescuers stands: there often is not much choice. When people really want the snake removed or killed, relocation seems the only option. When ecologists state that it would be better to kill the snake in order not to disturb the existing ecosystem of the other area's, that may be true, but not many snake handlers will be susceptible for their arguments.
In the meantime we need to try to educate people in areas where snakes occur. In schools, all children should be taught what the ecological function is of snakes, how to can live with them, venomous or not, and how they can avoid the risk of being bitten by venomous snakes. I think it would be an illusion to expect that many people are willing to accept the risks of venomous snakes in their neighborhood. But when most people are able to distinguish venomous from harmless snakes, and are willing to accept non-venomous snakes living around their houses, that would be a great leap forwards.
From time to time the discussion is reopened with new research. In 2017 there was an interesting article in Conservation India, involving mainly King Cobra location but discussing other snakes too. Here is the pdf. The paper on which this article is based, is Barve a.o. 2013.
Shine & Koenig 2001
Richard Shine, Jennifer Koenig, 2001. Snakes in the garden: an analysis of reptiles ‘‘rescued’’ by community-based wildlife carers. Biological Conservation 102 (2001) 271–283
Translocation: A Death Sentence. Into the Wild. Conservation Awareness, Wildlife Management, Wildlife Rescue, March 7, 2015. Internet: https://intothewildind.wordpress.com/2015/03/07/translocation-a-death-sentence/
Walker e.a. 2009
Mindy L . Walker, Jennifer A. Dorr, Rebecca J. B enjamin, and George R. P isani, 2009. Successful Relocation of a Threatened Suburban Population of Timber Rattlesnakes (Crotalus horridus): Combining Snake Ecology, Politics, and Education. IRCF Reptiles & Amphibians • Vol 16, No 4 • DEC 2009