Endangered species often don’t reproduce well in captivity or when reintroduced to the wild. Researcher Stephanie Courtney Jones believes that by studying the “pesty” traits that help invasive species reproduce well, and to be successful in multiple habitats, we might be able to help endangered species do the same.
Courtney Jones is studying an invasive mouse species to see how wild and captive animals differ over generations. While, for example, there are no external difference between captive and wild mice, internally, the more generations mice spend in captivity, the more their spleens, kidneys and gut length shrinks.
She wonders if such changes are plastic, and if by introducing challenges — different foods or behaviors — endangered species could be made to display more useful survival traits. Exploiting this plasticity might, for example, reactivate a latent trait that would allow a species that today lives in just one narrow habitat to live across a wide range of habitats, helping it adapt to climate change.
The researcher recognizes the challenges in her work. There are, for example, massive numbers of variables involved, and changing one specific trait can also unintentionally trigger the manifestation of other traits. And no one knows how altered endangered species might then interact within the environment.
Scientists have long known that invasive species possess “pesty traits” that benefit their spread. But what if similar, but latent, “pesty traits” could be triggered into action in endangered species to allow them to be more adaptable, maybe improving the success rates of captive breeding programs, or of habitat reintroductions?
It’s a “dangerous zoological idea,” agrees Stephanie Courtney Jones, a doctoral candidate at Australia’s University of Wollongong. She’s referring to the title of a Royal Zoological Society of New South Wales symposium held in 2013 that asked researchers to consider questions that pushed against the conventions of conservation science.
When Courtney Jones began pondering such ideas, she didn’t have a particular concept in mind. It took a fusion of unique work experiences and a six-month European “walkabout” before she finally arrived at her own “dangerous zoological idea” — an idea that drives her doctoral work today.
It started with her Master’s degree project on chickens, says Courtney Jones when she learned that you could alter the length of the birds’ intestines by varying the foods the captive animals ate. Another source of input was her work at a zoo, where she was trying to figure out how to coax endangered species to breed when they lacked the inclination. Meanwhile, her best friend was working on an Honors’ thesis, analyzing traits that enabled certain skink species to more successfully invade new places.
Courtney Jones intuited that all these things were linked: “We know invasive species have behavior changes that allow them to be very adaptable. We know we can feed chickens food that shortens their gut,” she explains. “So, why can’t we figure out what keeps captive animals from thriving? And then figure out how to change that phenotype [the observable characteristics] — morphologically or behaviorally?”
Mongabay: How did you turn that question into a Ph.D. study?
Stephanie Courtney Jones: I’m looking at changes between wild and captive mouse populations — an invasive species. Although research on captive breeding programs generally look at endangered species, I wanted to look at behavior and morphology changes. [Morphology is the branch of biology dealing with the forms of living organisms, and with the relationships between their structures]. And that involved dissection to — literally — figure out the guts of the problem, something I couldn’t do with an endangered animal.
So I compared behaviors and morphologies among three separate mouse populations, looking to see what happened over generations. One group was all wild mice that I caught at a very exciting field site – a pig farm. The second population [included] “captive” mice from an established breeding group, but originating from the same pig farm. Then I bred those captive mice and used their offspring, the F1 generation, as the third group. [An F1 generation is defined as the first filial generation comprised of offsprings resulting from a cross between strains of distinct genotypes].
In captivity, the mice are bolder and more active compared to wild animals, and even more so with subsequent generations. There’s also a loss of sex specific behaviors among the captive population (with females and males behaving in similar ways). When I looked at morphology, there was no external difference between populations when it came to body, tail and skull lengths. But internally, the more generations mice spent in captivity, the smaller their spleens, kidneys and gut length. All of those organs shrink in captivity because, presumably, it’s energetically expensive to maintain them if they aren’t getting used.
Mongabay: So captive-reared animals may be different from their wild counterparts in ways we can’t necessarily see, and those changes may make them less likely to survive in their natural habitat. Now what?
Stephanie Courtney Jones: The next thing is to figure out, firstly, whether these changes are plastic or fixed traits. Can the organs or gut expand over time?
If the changes are plastic, then maybe you can introduce challenges — different foods or behavioral tools — to induce this plasticity so the animals will display those wild traits again. But if those changes are fixed, we’ll need to look back at the parent generation and think about how influencing parent traits could influence offspring. Either way, you might be able to reduce the differences between the captive-bred and wild ones.
Figuring this out might help a species like the mountain pygmy-possum. Its current distribution is only on mountaintops in cool climate ranges, but the paleontological record shows they [once lived] in more temperate areas, with a much wider range than it has now. So there’s this idea [among pygmy-possum researchers] that if you can tap into that great-great-grandfathered past, and figure out how to activate that resilience to different climates, then they might be able to reintroduce them into other habitat pockets that might not be exactly the climate they are in –– or were in –– but where the animals might be able to persist.
So even though I’m working with an invasive mouse, this idea could help a non-invasive species like the pygmy-possum successfully live in new habitats.
Mongabay: What are the major challenges in your work?
Stephanie Courtney Jones: Four years ago if you asked me what I would be doing with my PhD, I would have told you that I would be tapping into this idea, reintroducing endangered species, and then seeing what happened. “Free the phenotype” was going to be my gimmicky thesis title, along the idea of Elsa, the lioness in “Born Free.”
But the reality is that I haven’t been able to reintroduce a single animal, partly because mice are a pest species in Australia, but also because it was a bit naive to think I could achieve everything I wanted with this idea without a solid understanding of the fundamental changes occurring in captivity. I’ve only just scratched the surface and there’s so much more to it than what I thought when I started.
You can manipulate one type of behavior, [for example,] but you don’t know how it will affect others. I focused on boldness and activity as behavior traits in the mice, but I know there’s a whole suite of other things that are important for an animal when they’re getting reintroduced. The time frame is also a factor. Are you looking at behavior immediately after release? For a couple of days? Or the rest of the [animal’s] life span?
It’s mind boggling sometimes [to try and consider all the factors involved]. Nature knows best and does it brilliantly. So when humans try to manipulate these systems we really don’t know what were doing.
Still, I think we should be more experimental. I have colleagues who are reproductive biologists in zoos, working with endangered species, and they are looking at new approaches to mate choices. Rather than [the scientists] controlling who mates with whom to maintain genetic diversity, they are actually saying: Let the lady have a choice, maybe she knows best. And that’s created more reproduction success, more litters.
When I hear that, my question is: what’s happening with the next generation? How are they performing? We’re only beginning to understand what we’re doing with animals in captivity.
For more on the topic:
Stephanie Courtney Jones Blog: https://zoologistjones.wordpress.com/
Chapple D, Simmonds S, and Wong B. “Can behavioral and personality traits influence the success of unintentional species introductions?” Trends in Ecology and Evolution, 2012. Jan; Vol. 27(1), pp 57–64.
Chapple D, Simmonds S, and Wong B. “Know when to run, know when to hide: can behavioral differences explain the divergent invasion success of two sympatric lizards?” Ecol Evol. 2011 Nov; Vol.1(3): pp 278–289.
Courtney Jones SK, Munn AJ, Penman TD, and Byrne PG. Long-term changes in food availability mediate the effects of temperature on growth, development and survival in striped marsh frog larvae: implications for captive breeding programmes. Conservation Physiology, Vol. 3 (1):cov029.
Courtney Jones SK, Cowieson A, Williamson S, and Munn A. No effect of short‐term exposure to high‐fibre diets on the gastrointestinal morphology of layer hens (Gallus gallus domesticus): body reserves are used to manage energy deficits in favour of phenotypic plasticity. J Anim Physiol Anim Nutr, (2012). Vol. 97: pp 868–877.