Adaptation of the Fennec Fox to the Desert

How the fennec fox (Vulpes zedra) has adapted to the desert environment

The fennec fox is the smallest member of the Vulpes genus (formally in the Fennecus genus) only weighing 2.2 – 3.3 lbs. It is highly distinguishable by its huge ears measuring 6 inches, and a body length of up to 16 inches. It is a nocturnal animal that stays in its burrow and rests for the hottest parts of the day (The Nature of Wildworks, 2014.). It is a highly social animal and lives in family groups of up to 10 individuals (Fox, 1975). Formerly in the fennecus genus, it was later re-classified into the Vulpes genus which is the main taxonomic group of all foxes. Its geographical range is the north Sahara and Arabian deserts. The fox is under decline due to being hunted for the fur and pet trade which has had significant impacts on the wild species (The Nature of Wildworks, 2014.) The fennec fox has many adaptions to living in a desert environment. These can be broken down into 3 categories; Morphological, Physiological and Behavioural.

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Morphological

Morphological adaptions are changes in the animal’s structure that helps it adapt to the extreme conditions of the Saharan dessert. One of the most significant morphological adaptations that the fennec possesses is its large ears. The ears are used to dissipate heat and maintain the optimum body temperature of the animal (Wathen, et al., 1971). The ear needs to be large to have a large surface area for heat dissipation. The statement that these actually cool the animal is not entirely true, they do not cool the animal and lower its body temperature, but instead maintain the optimum body temperature. In a study on jack rabbits, the ears were found to dissipate nearly 100% of all metabolic heat at air temperatures of only 30°C (Wathen, et al., 1971). This is only possible if the temperature of the fox is above the environmental temperature. The ears also play a critical role in nocturnal hunting (Wathen, et al., 1971). The large pinnae of the ear help direct low level sound into the ear which gives the fennec acute hearing allowing directional hearing (Ewer, 1973). This is a key adaption for hunting at night due to the low light levels, thus giving the fennec the ability to hunt effectively at night using sound as well as excellent night vision.

The feet of the fennec are adapted to walking on the hot sand by having hairs covering their fleshy foot pads (Ewer, 1973). This prevents the foot from actually touching the scolding sand and will prevent injury when the fox is digging its burrow and walking across the hot dessert floor. The front paws are specially designed for digging burrows which the fennecs live and breeds in (Ewer, 1973).

The fur of the fennec like most dessert animals is vital to coping with desert life. Not only does this insulate the animal, but studies have shown that the light fur of the animal can also reflect the solar radiation, therefore lessening the impact and reducing the heat load on the animal (Dawson & Brown, 1970). This is most true in the fennec fox due to its sandy coloured or sometimes white fur. Meanwhile the thickness of the fur is a protection from the solar radiation of the skin. By creating this barrier, the fur prevents any damage to the skin from direct solar radiation. This is because the fur, as said before, partially reflects the solar radiation while the thicker deeper fur absorbs the heat (Dawson & Brown, 1970). The heat absorption also helps the fox survive the freezing dessert nights while it feeds, by preventing the fennecs core body temperature from dropping too low.

Physiological

Physiological adaptions are changes in the animal’s system processes to enable them to adapt to changes in the environment. These changes enable the fennec to adapt to the extreme environment of the North African deserts. Carnivores, just as the fennec, are found in a number of deserts around the world. A major challenge that these organisms face is the replenishment of water. The fennec gains its water requirements solely from having mostly a carnivorous diet. The fennec, by eating alone, can maintain its water balance for over 100 days without having to drink (Vaughn, et al., 2000). This is done by the fennec having very concentrated urine that uses the least amount of water possible to function. This conserves a vast amount of water and coupled with its very low evaporate loss. Therefore it rivals small desert rodents in its water conservation (Vaughn, et al., 2000). This relates to selective predation and an ability to feed on a wide variety of food stuffs, while being able to become more economical with its metabolic water.

The adaption of having a low basal metabolic rate is crucial to survival in dessert conditions. The fennec is no exception to this; it has one of the lowest BMRs of all Vulpes species of 60.7 percent (Golightly & Ohmart, 1983). This means at rest the fox only uses the minimal amount of water needed to survive. This adaption allows a minimalized endogenous heat load which conserves metabolic water. This saving of water becomes critical in the desert due to the low precipitation levels and therefore having the adaptation of a low BMR helps maintain any dietary water acquired and conserves it.

Behavioural

Behavioural adaptations are changes in the animals conduct help it survive in a certain environment. Previously, little was known about the fennec foxes diet. It was previously thought that they were primarily insectivores and had barely any variety in their diet. However, a new study has shown that they are actually opportunistic feeders with food items being mostly insects, but it also feeds on small mammals and even plant material (Brahmi, et al., 2012). The study also shows that locality and abundance of food can also change the feeding behaviour of the fennec. This adaption is critical to the survival of any dessert animals. The ability to feed on many different food sources opens up many more niches and availability for the animal to survive and feed (Brahmi, et al., 2012).

Panting is an adaption that requires short shallow respiration and is solely used in heat dissipation. Panting makes use of evaporative cooling of the mouth, lung and nasal mucosa. This is a very effective way of cooling down without having to sweat. This main advantage over sweating is that in sweating there is salt loss, while in panting there is not (Vaughn, et al., 2000). This is key to the survival of the fennec because of the shortage of food; therefore the fennec cannot regain the salt quicker than the animal uses up. If the fennec sweated this could become a huge problem, so it has overcome this problem by making use of the more efficient panting for heat dissipation (Vaughn, et al., 2000).

Fennec fox families live and thrive in burrows; these help counteract the daily effects of high temperature and low humidity of the desert days. They provide shelter from sun exposure and the highest temperatures of the dessert day. A study in tortoises shows that burrows provide a great place to refuge in a desert environment. The study showed that the burrow at 10:00 -12:00 hrs had much higher humidity and lower temperature than the external environment (Bulova, 2002). This lowers the total evaporate water loss which helps the animal, in this case the fennec, conserve metabolic water, which is key to desert survival. Fennecs therefore make use of the much more stable and milder environment inside the burrow. This helps shelter the fennec from extreme conditions and helps conserve water. This is due to the soil temperature maintaining stability no matter what the conditions are outside. The burrow controls the internal environment due to the thermal insulating properties of the soil (Reichman & Smith, 1990). Therefore the burrow is cooler during the day and warmer during the freezing desert nights.

Conclusion

To conclude there are many adaptations the fennec has; may that be morphological, physiological and behavioural. The adaptations are a necessity to survive in such an extreme climate, such as the dessert; with high heat loads during the day, freezing temperatures in the night, food and water sources are scarce. The adaptions that the fennec utilises all boil down to protection from the incredible temperature change in the dessert, by having large ears to dissipate heat and fur that can reflect but also absorb the heat. This gives protection from solar radiation during the day, and insulation during the night. The other main reason for having many complex adaptations is to conserve water. The fennec’s metabolic water level is maintained by having a low BMR which uses less water in metabolic activity at rest, and also the concentrated urine which reduces the loss of water via waste. In my mind the fennec fox is perfectly adapted to cope with the extremes of desert life, by controlling its water conservation and body temperature.

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References:

Brahmi, K. et al., 2012. First quantitative data on the diet of the fennec fox, Vulpes zerda (Canidae, Carnivora), in Algeria. Folia Zoologica, 61(1), pp. 61-70.

Bulova, j., 2002. How temperature, humidity, and burrow selection affect evaporative water loss in desert tortoises. Journal Of Thermal Biology, 27(3), pp. 175-189.

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Wathen, P., Mitchell, J. & Porter, W., 1971. Theoretical and Experimental Studies of Energy Exchange from Jackrabbit Ears and Cylindrically Shaped Appendages. Biophysical Journal, 11(12), pp. 1030-1047.

Harvard – Anglia 2008