Many of
Earth’s plant and animal species are at imminent risk of extinction. But with
the resources necessary to conserve them so sorely limited, where should
efforts be focused? The term “ecological triage” has been coined for
such decision-making, after the system invented by French army medics to sort patients by
the urgency of their need. This borrowing of metaphor from the Napoleonic and
World Wars is not accidental: in envisaging the damage done to nature by
humanity, you are to think of cannonballs and scorched earth and mustard gas.
The header image by Jamie Grant-Fraser shows White-faced Whistling Ducks (Dendrocygna viduata) responding to the appearance of a Madagascar Harrier-hawk (Polyboroides radiatus).
I recently returned from a short stint of fieldwork in Madagascar. The purpose of our trip was to run some behavioural tests of echolocation in tenrecs but things didn’t exactly go according to plan. Therefore we had plenty of time to explore and experience some of the wonders of the 8th continent.
Here’s a few of our wildlife highlights…
Our friend from the shower
Enormous spider webs which span an entire river bed!
I’ve been studying tenrecs for almost two years. I’ve read about them, watched video clips and handled hundreds of dead specimens. However, within that time I only met two live individuals, both of which were captive zoo animals. That’s all changed. I’m now well acquainted with a variety of tenrec critters. It turns out they’re a quiet bunch.
Just slightly excited to be holding a live tenrec!
My supervisor, Natalie, and I spent two weeks in Madagascar working with a research team from the Vahatra Association led by Steve Goodman. The purpose of their trip was to conduct a disease transmission study in bats and small terrestrial mammals study at Ambohitantely Special Reserve, a protected, upland native forest north west of Antananarivo.
Looking down onto Ambohitantely forest; not a bad place to work…
We tagged along on the trip to run behavioural experiments to test whether there’s evidence for echolocation in the shrew-type (Microgale) tenrecs. Armed with a bat detector and an adjustable maze, my plan was to record the tenrecs’ calls as they move through their environment in search of a worm food reward at the end of the maze.
Our “experimental chamber”; the maze box (covered with material in the bottom right of the picture) set up in a shower cubicle!
I had envisaged many potential problems with the experiment. How would we be able to filter out interesting noises from background sounds? Would the noise of the animals moving around mask out the true vocalisations? I didn’t, however, foresee the problem with which we were faced; they didn’t make any noise whatsoever, zilch, not a peep.
Pockets bulging with tenrecs!
We tried multiple methods to coax some sound out of the furry creatures. The animals were kept warm in Natalie’s increasingly bulging coat pockets. We tried to entice the animals using juicy worms as proverbial carrots. We experimented with placing pairs of individuals in the box at the same time hoping to overhear some tenrec chat. We also eliminated technical faults as a possible cause by testing out my detector on the bats flying around camp at night. All to no avail.
Microgale dobsoni; “I don’t want to produce any sound and you can’t make me”
I think they were holding out on us. The other, more experienced field researchers had heard tenrecs squeaking while foraging. The previous work on echolocation in tenrecs which inspired my experiments includes recordings of one species of Microgale so the animals are certainly not mute. I think our empty sound files are an unfortunate consequence of our experimental protocol. Existing research on possible echolocation in shrews and tenrecs used captive animals under highly controlled experimental conditions. We, however, were constrained by time and resources to an artificial experimental set up so it’s unfortunate but not entirely surprising that things didn’t go according to plan.
Still, the trip was far from wasted. Studying and observing living animals is just a tad more exciting than their museum counterparts and I now have enough pictures of tenrecs to last for a lifetime of presentations. We met some extremely interesting and knowledgeable researchers and we had the opportunity to work in a remote, beautiful and exotic place.
Furthermore, our failed experiments left time to go and explore other areas as tourists; expect our encounters with Indri, mouse lemurs, chameleons and enormous spiders to be coming soon…
Author and Images: Sive Finlay, sfinlay[at]tcd.ie, @SiveFinlay
I have all the essentials; insect repellent, tent, flat pack wooden box, bat detector, three metres of blackout curtain material… Not the most usual of packing lists admittedly but all necessary items for the trip ahead.
I’m going to study tenrecs; cute mammals which are the subject of my PhD. I’m interested in convergent evolution between tenrecs and other small mammals. So far I’ve been focusing on morphological convergence – work which has involved trips to beautiful museums and taming the dark arts of morphometrics. The primary aim of my research is to assess the evidence for morphological and ecological convergences among tenrecs and the mammals they resemble. Technically I could complete these aspects of the project without ever seeing or dealing with the live animals. But where’s the fun in that?! I’m also interested in behavioural convergences among tenrecs and other mammals, particularly reports of the abilities of some tenrecs to echolocate.
Some shrews produce echolocation calls by clicking their tongues. More recent work indicates that shrews seem to use these clicking calls primarily for navigation within their habitat rather than communication. Intriguingly, there is evidence that at least three species of tenrec; the lesser hedgehog tenrec, lowland streaked tenrec and Dobson’s shrew tenrec, can also echolocate. The animals seem to use their tongue clicks for navigation. The stridulation sounds produced by specialised spines in lowland streaked tenrecs and juvenile tail-less tenrecs have also been linked to having an echolocatory function but immobilising the spines doesn’t seem to affect the animals’ abilities to navigate by sound.
These early experiments are tantalising evidence of intriguing behavioural convergences among shrews and tenrecs. However, limitations of 1960’s acoustic technology and the ever so slight changes in standards of experimental practice (blinding animals with cement doesn’t go down so well with modern ethics boards!) mean that the study of echolocation in tenrecs is ripe for further exploration.
Hence my unusual packing list. My plan is to place wild-caught tenrecs within a box that can be converted into a maze of various layout and complexity (I’m extremely grateful to our super technician, Peter Stafford for making an adjustable maze which can be flat-packed for travel to Madagascar!).
Tenrec maze!
Using a bat detector, I’m going to record the sounds produced by the animals both when they’re “at rest” just in the empty box and when faced with the task of moving through the maze to reach food at the other end. I’m going to observe and film the animals moving through the maze, both in daylight and under red-light conditions in darkness (hence the blackout curtains) and record the sounds they produce as they move. The idea is to test whether the animals’ call patterns (structure/frequency of calls) changes as they navigate their way past an obstacle in the maze. Bats are known to modulate their call frequencies when they hone in on their prey or to navigate their way past obstacles. I want to test whether there’s similar call modification in tenrecs which would provide evidence that the animals are actually using their echolocation sounds for navigation. It would be fascinating to understand more of how tenrecs use echolocation and to test whether other tenrec species can also echolocate.
It all sounds quite straightforward but I’ve experienced some of the vagaries of fieldwork in the past and I’m anticipating many more problems to come. I’ve received advice and war tales from researchers who have tried to study echolocation in shrews only to be thwarted by problems of distinguishing the animals’ calls from background sounds or the noise of the animal’s claws on a wooden base. Similarly, the tenrecs may not want to cooperate with my idea of moving from one end of the maze to another. I’m hoping that a nice juicy earthworm at the other end will act as the metaphorical carrot but there’s no way to know until we actually try it out. Furthermore, it might be difficult to distinguish sounds that say “I’m scared of being in this box” from sounds that the animals are using for navigation. Similarly, since we have neither the option nor inclination to experimentally blind or deafen the animals we won’t be able to completely exclude the possibility that the animals are using other sensory cues aside from acoustic navigation.
Even still, I’m hoping to get results which demonstrate the range of calls produced by tenrecs and which provide clues into how the animals use their acoustic behaviour to their advantage. Echolocation has involved independently in different animal lineages. Most interestingly, there is even clear evidence for convergence at the level of genetic sequences. Hopefully the data I gather over the next few weeks will add to our understanding of this fascinating story of convergence among tenrecs and other mammals.
And maybe we’ll spot a few lemurs on the way…
Author: Sive Finlay, sfinlay[at]tcd.ie, @SiveFinlay
Tenrecs are one of the most interesting and fascinating mammal groups yet many people have never heard of them. They are one of only four mammalian groups to have colonised Madagascar, a land filled with evolutionary curiosities.
Tenrecs are a striking example of convergent evolution. From a single colonising ancestor, tenrecs have evolved into incredibly diverse species which resemble moles, shrews, hedgehogs and even otters! Contrary to appearances, tenrecs’ closest relatives are actually the golden moles and elephant shrews (Chrysochloridae). However, physical convergences are so strong that early taxonomists didn’t recognise tenrecs as being closely related to each other, an easy mistake to make when you look at this picture from Richard Dawkin’s 1996 book “Climbing Mount Improbable”.
Convergent evolution in tenrecs. The Algerian hedgehog, Erinaceus algirus (a), is a close cousin of the shrew hedgehog, Neotetracus sinensis (b). The greater hedgehog tenrec, Setifer setosus (c), is a close cousin of the long-tailed tenrec, Microgale melanorrhachis (d)
In addition to being great species for studying convergent evolution, the tenrec family includes a whole host of quirky traits. For example, the common tenrec (Tenrec ecaudatus), an animal which is only around 30 cm and 2kg, holds the record for the largest litter size of any mammal at an astounding 32 babies!
My personal favourite tenrec oddity is the unusual means of communication found in the lowland streaked tenrecs (Hemicentetes semispinosus). These cute critters are covered in spiny quills, a special set of which are used as a stridulating organ. Reminiscent of grasshoppers or crickets and uniquely among mammals, these tenrecs rub the quills together to produce sound which then allows them to keep in contact with their family group. This clip from the David Attenborough BBC series on Madagascar shows the stridulating tenrecs in action.
In short, tenrecs are an awesome family filled with evolutionary oddities yet they remain relatively understudied and poorly understood.
In my PhD work, I’m particularly interested in measuring the extent of convergent evolution in tenrecs and figuring out the reasons why they have evolved to be so similar to unrelated species. I’m also intrigued by early behavioural experiments which showed that 3 species of tenrec use echolocation. I want to test whether other tenrec species also echolocate and hopefully link this behavioural convergence to genetic similarities in “echolocating genes” which are conserved in whales and bats.
In the meantime, a charming children’s book gives the perfect excuse for some light, PhD-related extra reading!
