Lizards are victims of global warming
With global warming, lizards are struggling to keep cool. Even pregnant women are strongly disturbed by the heat, according to a study published in a scientific journal Oikos. They have difficulty lowering their temperature at night, and the risk of stillbirth is greatly increased. Similarly, heat increases energy needs, so you need to eat and drink more. Other evils threaten these reptiles: the disappearance of invertebrates – their main food source – increased periods of drought and the destruction of habitats. Another study, recently published in Pnas, revealed that small lizards exposed to extreme heat showed signs of premature aging. Ultimately, all these disturbances could lead to the extinction of the animal in the regions most exposed to heat in the south of France.
The small lizard species under study is called Zootopia viviparous. A serious diurnal, it measures 5 to 8 centimeters and appreciates cool and moist places such as swamps, meadows or wet meadows in northern Eurasia. Its range is large: from Brittany to Japan, through Siberia. “ In France it occupies the mountains, especially the Massif Central and the Pyrenees, where it finds cool conditions favorable to it. », explains Andreaz Dupoué, researcher and animal expert at Ifremer. However, with climate change, scientists have noticed that this species has disappeared in some places. “ especially at low altitude » where the temperature is higher.
A cool night’s rest is essential
To better understand how the animal responds to climate change, they captured pregnant females on the Plateau des Millevaches in Limousin. Females were housed during two to three months of pregnancy and until birth “ climate chambers » at the Chizé Center for Biological Research (CEBC), in Deux-Sèvres. They then lived in different environments: more or less hot (31°C for 4 or 9 hours during the day and 17°C or 22°C at night) and more or less humid (optional or limited water ). Between mid-July and early August, 1-12 lizards are born from each female. Later, the females were released into the natural environment with their cubs.
The researchers first observed that females exposed to high temperatures (day and night) appeared hungrier and ate more grasshoppers. A situation “ problematic in the context of global invertebrate decline », note the authors. They also noted that the gestation period of females is significantly shortened when daytime temperatures are high. But above all, it’s hot at night “ caused the most negative effects »emphasizes researcher Olivier Lourdais CEBC. These women had more weight loss after delivery (and was aggravated by dehydration) and had a higher risk of stillbirths or unfertilized eggs (+26). %). In effect, “ rest periods at night are important. The animal needs refreshment to restore favorable levels of metabolic activity. »
Protection of natural habitats, a remedy for heat
Another surprising discovery: with global warming, some populations of lizards are already being born “ old ». Researchers have discovered aging markers in their genomes that previous generations did not show. In populations exposed to abnormally warm temperatures, “ most newborns inherit telomeres — the ends of their chromosomes that should shorten with age — that are already too short, meaning they are born physiologically old and have little chance of reaching puberty. »explains Andreas Dupoué, co-author of the study.
This phenomenon is cumulative: over generations, telomere length shortens as new climate extremes are encountered. So much so that researchers fear the lizards are reaching a breeding point where they will no longer reproduce and simply slide toward extinction. A hypothesis that could explain the local disappearances already observed.
Outside Zootopia viviparous, all lizard species can be affected. Global warming alone will not solve the fate of reptiles. “ Soils and peat bogs that provide a cool and humid microclimate are favorable habitats for these species. »Olivier Lourdais says. Therefore, animals could take shelter there. In order to preserve biological diversity, the scientist assures that it is important to protect different natural environments and habitats. But human activity, especially intensive activities, tends to do so “ simplify landscapes: hedgerows disappear and landscapes become increasingly open and degraded. ». The bottom line: the effects of global warming and drought on wildlife are exacerbated by habitat degradation. since XIXe century, about 90 % moors and 50 % of peat bogs in Europe have disappeared due to drainage, cultivation and tar.