Some desert creatures may be able to copewith climate change better than expected25 May 2018

An adult gecko with a backpack containing an RFID tagattached to the lizard's skin. The RFID tag transmits itslocation and the gecko's body temperature. Credit:Annegret Grimm-Seyfarth, UFZ

The world of reptiles may well include creaturesthat are more spectacular than the Gehyravariegata, but nevertheless, this small nocturnalgecko has managed to make a couple offascinating new contributions to the discussionabout the ecological consequences of climatechange.

These geckos are small grey- or brown-skinnedlizards that grow to around five centimetres andspend their lives in the deserts of Australia. Thehollowed-out trunks of eucalyptus trees are theirpreferred hiding places. After spending the nighthunting insects, this is where they seek refugefrom the heat in a climate where temperatures canoften climb to more than 40 degrees Celsius. And itis in exactly these deserts where climate scientistsexpect to see even more extreme conditions in thefuture. They are forecasted to become even hotterand drier worldwide. So how will the uniqueanimals and plants that live in these ecosystemscope with these new challenges? This was the

question the researchers set out to investigate,using this little gecko as a representative of othernocturnal desert inhabitants.

Prof. Klaus Henle, head of the Department ofConservation Biology at the Helmholtz Centre forEnvironmental Research, began collecting dataabout Gehyra variegata as far back as the 1980s.Working in the Kinchega National Park in EasternAustralia, he and his colleagues have beencatching, measuring, photographing, tagging andthen releasing reptiles for more than 30 years.

The researchers at the Helmholtz Centre forEnvironmental Research then collated thisinformation with weather conditions in the nationalpark, and also with global climate phenomena.Their findings are surprising, to say the least. Asbiologist Annegret Grimm-Seyfarth said, "Weexpected the higher temperatures and greaterdryness to have a negative effect both on theindividual geckos and on their populations." Afterall, even lizards need a certain amount of moistureto ensure that their eggs develop properly, and toenable them to moult when they need to. If they dryout completely, they will die. And the same is alsotrue if excessive temperatures cause them tooverheat. "But our investigations revealed that ourgeckos grow and survive particularly well in thevery hottest years. In fact, they are generally inbetter condition, and their populations grow ratherthan fall."

But what could be the reason? To discover this,Grimm-Seyfarth carefully observed the lizards'behaviour and measured their body temperature.

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The biologist Annegret Grimm-Seyfarth, searching for agecko's daytime hiding place in a eucalyptus tree. Theradio antenna locates individual creatures that arecarrying an RFID tag. Credit: Jean-Baptiste Mihoub, UFZ

At night, she used an infrared thermometer, whichcan measure temperature at a distance, to locatethe creatures while they were hunting. And then, tofind where the geckos were hiding during the day,the scientists used tiny passive transmitters, similarto those used as ID chips for dogs. These chips areusually implanted under the skin. But when the tinyreptile is only five centimetres long, this isn't reallyfeasible. So, the scientists created miniaturebackpacks for the geckos to wear, which keep thechips close to their skin. The researchers then usea radio antenna to locate the chips. The chips notonly reveal where each lizard is, but also transmitits body temperature. Despite the tremendousdaytime heat in the desert, the scientistsdiscovered that the geckos don't search outparticularly cool places to hide. They prefer theirrefuges to have a temperature between 30 and 35degrees Celsius. As Grimm-Seyfarth said, "Thecreatures need these high temperatures so thatthey can digest their food properly." Consequently,they also crawl around in branches that areparticularly exposed to the sun. To herastonishment, Grimm-Seyfarth also found that, incooler years, the geckos left the safety of their treeand deliberately sat out in the sun to bask in itsheat. But searching for enough warmth also takesenergy. And, if the search is unsuccessful, thegecko can't digest its food properly. This might be

the reason that cooler years had a negative effecton the geckos.

However, even having the perfect temperaturerange isn't any good if it's also too dry. This doesn'tjust cause physical problems for these creatures. Inparticularly dry periods, there are also fewer insectsfor them to eat. As expected, geckos experiencereally hard times during periods of drought. But it'snot just local precipitation levels that are thedecisive factor. Every few years, the La Niñaweather phenomenon brings torrential rainfall to theeast coast of Australia. Months later, the riversbring the resulting flood waters to the desert,increasing humidity levels and creating anabundance of insects. As Grimm-Seyfarth said,"These lizards are affected by local conditions andglobal climate phenomena alike. We need to lookbeyond the horizon of a particular area if we wantto make an accurate prediction about the future ofits inhabitants.

Until now, all the evidence indicated that thegeckos would face problems caused by droughtrather than by heat. But now, we have discoveredthat they can also compensate for this, to a certainextent. The study shows that, although individualcreatures become thinner in years of drought, theirpopulation levels remain constant. This is becausethey scale back their growth and reproduction ratesin hard times," explained Grimm-Seyfarth. They canthen concentrate all their efforts on surviving intothe next year. Thanks to their exceptional longevity(up to 28 years in some cases), these creaturescan afford to lose a few reproductive cycles withoutany particular problem. And when conditionsimprove again, they can make up for lost time.

Therefore, even if climate change causesdeterioration in living conditions for these geckos,they're hardly likely to die out immediately. And,according these evaluations by the scientists at theHelmholtz Centre for Environmental Research,these findings could also apply to other long-liveddesert dwellers. However, this is in no way a simplecarte blanche for letting climate change justhappen. "If there are several very dry years insuccession, the creatures will no longer be able tocope," said Grimm-Seyfarth. At some point, eventhe hardiest survival specialists will be

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overwhelmed.

More information: Annegret Grimm-Seyfarth etal, Some like it hot: from individual to populationresponses of an arboreal arid-zone gecko to localand distant climate, Ecological Monographs (2018).DOI: 10.1002/ecm.1301

Provided by Helmholtz Association of GermanResearch CentresAPA citation: Some desert creatures may be able to cope with climate change better than expected(2018, May 25) retrieved 15 February 2022 from https://phys.org/news/2018-05-creatures-cope-climate.html

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