In the drylands, animals, like plants, are confronted with two major problems: resistance to extreme heat and the lack or absence of water. While heat and drought are factors that limit the development of animal populations, maintaining animal populations in the drylands is linked to physical adaptations (morphology, physiology and behaviour) that compensate for the negative effects of these factors.
Adaptations that reduce
the effects of heat
The majority of animal species (invertebrates, reptiles, rodents, sloths etc.) live at ground level where temperatures are at their highest. Here, temperatures can reach 57°C yet animals cannot survive temperatures beyond 42°C, so how do they protect themselves?
Certain animals resist heat constraints by adaptation and evolution:
© Michel Le Berre
5. Young Kobus kob kob antelope. Throughout Sub-Saharan
Africa, different species of antelope are appreciated by hunters
for their ‘bushmeat’. However, their relentless hunting
threatens the well-being of the population.
© Amélie Dupuy
6. Frog adapted to drought (Hyperolius nitidulus). During
the dry season, the frog changes colour becoming white in
order to reflect light, heat and to conserve humidity.
© Amélie Dupuy
Compenstating for water scarcity
During the dry season in the drylands, vertebrates can lose up to 30% of their body weight in water (dromedary, rodent) and amphibians, from 40% to 50% (frogs, toads etc.). Certain species compensate for this by reducing evaporation (thanks to their waterproof skin) and the loss of water by excretion: urine is very concentrated and their faecal matter is dry, as seen in jerboas for instance. They also recuperate water from night mists and from the humid walls of their burrows. Certain species survive without having to drink on a daily basis (moufflons, dromedaries and goats) while others can transform starch found in grain into water (rodents).
All these adaptations enable animals to live in the hostile arid environment and are characterized by genetically inherited features acquired over a long period of evolution. Their co-existence with other animal and plant species provides an important balanced ecosystem that maintains life in the drylands and is a valuable resource to the populations that depend on them. The conservation of these organisms is thus of vital importance and a valuable asset to the development of these particular regions.
Choose 5 animals found in your region. Observe them if you can and find out as much information as possible about them, in books or by asking older members of your family.
Make 5 animal identity cards that describe their characteristics: family group, species, geographic location, behavioural and physical characteristics etc.
Organize a miming game using the above identity cards. Mimic an animal by imitating certain adaptations to heat, water shortage (behaviour, specificity of limbs, etc.)
The class must guess
Which of the following animals have developed adaptations to heat to over the course of evolution:
Draw an imaginary animal that possesses all the characteristics necessary to resist heat and drought.
Give it a name and present it to the class.