The Science of Spots

Rudyard Kipling’s Just So Stories ‘How the leopard got it spots’ tells us that the feline had them painted on so it could blend into the forest ‘full of trees and bushes and stripy, speckly, patchy-blatchy shadows’. While we know that this is not true, he was close in his assumption in that the coat pattern is reflective of the cats primary environment – cats that hunt in open areas and are active mainly during the day, like lions, tend to have plain coats. Ones that dwell and hunt from trees, forested areas or at night, like leopards or jaguars, tend to have dappled, spotted coats, or in the case of tigers stripy coats.

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Connect the spots – Image – M-H JeevesChemistry World

It is known that coat and colors patterns like the leopards evolved for camouflage and, William Allen a researcher at the University of Bristol reinforced this theory after completing a study of coat pattern images from 37 different types of wild cats. The data from the images along with “information concerning the size of each species, its habitat, characteristic behaviors and more, was then plugged into a mathematical model of pattern development. ” It was determined that spots were most common in species that spend greater amounts of time moving in trees, and in those that are active at lower light levels.

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©Tori-Ellen Dileo – It’s all about genetics. Every leopard has a different pattern – female South Luangwa NP, Zambia

Beside environment, there are likely more factors involved which influence the coat patterns of wild cats as they don’t always exactly mirror the animals surroundings. A few anomalies include the cheetah, which prefer open habitats but have retained their spots, this is thought to be the case because they rely mostly on speed, as opposed to camouflage, for hunting. The overall consensus is that coat patterns seem to have evolved to correspond to environments as well as how the wild cats behave within their specific environments.

Allen told BBC News that “When you place cat patterning over the evolutionary tree of cats, you can see that patterning emerges and disappears very frequently within the cat family, which is kind of interesting – it suggests that perhaps particular genetic mechanisms can solve very different appearances of cats.”

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Image ©Tori-Ellen Dileo – Clever cats at home in trees and perfectly camouflaged in low, shady light – Male Leopard South Luangwa NP, Zambia

The leopards beautiful spots are more than skin deep and the mechanism responsible may have a lot to do with chemistry. Alan Turing a mathematician and founder of computer sciences, proposed that chemistry had a role in forming patterns like those on a leopards coat. In Turings only published paper on chemistry, he put forth a set of equations which attempted to explain the patterns seen on leopards. The elements in this process contained and ‘activator’ whose presence caused cells to produce pigmented black hairs and, an ‘inhibitor’ that would cause cells to create white hairs.” If they were strongly different it would enable a pattern to grow. Turing was able to demonstrate mathematically that these “simple components could account for a wide range of patterns and, a subtle tweaking of the parameters could alter the pattern to create spots, stripes, swirls, splodges or other markings.”

Much later on Turing’s theory would be used by biologists to support the hypothesis about other patterned animals. Chemists would eventually recreate an example of Turing’s pattern in a lab using a gel which developed a pattern of “yellow dots on a blue background”. It is now acknowledged that the science of spots has turned out to be more complicated than first presented and researchers admit that it does not fully solve the riddle of how the leopard got its spots, even though the theory is still considered a major contributor to determining how patterns form.

For more on the science of spots I highly recommend taking a listen to the BBC Radio 4 Just So Science episode which talks about the science and math behind the patterns and reading Plus Magazine’s Some Just So Stories of animal patterning.

Wolf-Deer

Many years ago on a trip to Kenya I was very fortunate to see a serval on a night drive in Amboseli National Park. The image while grainy reminds me of how beautiful, elegant and perfectly camouflaged this animal is for its environment. It was the cats glowing eyes that gave it away and, as we stopped to watch, he or she turned around and gave one over the shoulder glance before silently padding off into the tall grass under the cover of darkness.

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The name Serval is derived from a  Portuguese word meaning “wolf-deer”  or “deer-like wolf”

Servals (Leptailurus serval) are a medium-sized lesser cat, not to be grouped with the bigger cats even though they have been called miniature cheetahs, weighing between 30 to 40 pounds. Some of their distinguishing characteristics include tawny coats with black strips, splotches, spots, and, large oval ears which enable them to detect the slightest sounds and target small prey animals in the grass or in the ground. They also have the longest legs, which make them excellent acrobatic jumpers and hunters, for body size of any of the cats and are most at home in grassland and moist habitats such as reed beds and marshes, but are found in a variety of habitats throughout Africa except tropical rain forests and the Saharan desert. In North Africa a few isolated populations are said to exist in both Morocco and northern Algeria but it is thought they number less than 250 individuals, isolated in vulnerable sub-populations of fewer than 50. Therefore it is generally recognized that servals are critically endangered north of the Sahara.

If spotting a serval is lucky then catching a glimpse of the very rare melanistic serval is magic and, there are only 4 locations in Eastern Africa where you might be able to have this experience.

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Image © Alison Mees – “Interestingly, the serval spotted by Mees was foraging in the lowlands of  Tanzania’s Serengeti National Park suggesting that either these black cats are moving out of the mountains, or they are spreading their melanistic genes to populations that live at lower elevations. We’ll leave that to the experts to figure out.” via Earth Touch News Network

Melanism is a genetic condition in which an animal has an increased development of black pigmentation in the skin and hair, and even though the cause of  the condition still remains unknown, it is thought that the darker coloration helps retain body heat and provide a type of survival mechanism. Many other feline species, including bobcats, have exhibited melanism and it appears in about 13 of the 37 known feline species worldwide.

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Image © Christian Boix – Melanistic Serval in Mkomazi National Park, Tanzania via Africa Geographic

Servals are typically a solitary species with pairs only coming together for a few days to mate. The female will give birth to a litter of kittens approximately 74 days later and about a year later she will chase her young from her territory allowing female offspring to stick around a few months longer than the males. Seeing two servals together wouldn’t be surprising if you happen to be at the right place at the right time, however if you happen to witness the meeting of a regular colored serval and a melanistic serval – that would be something truly special and rare.

This is exactly what happened to Jeremy Goss, conservationist and wildlife photographer, while on a night game drive in Kenya. It was unclear if this was a courtship or simply two servals greeting one another, regardless the photographs and video show an unforgettable meeting between the two cats.

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Image © Jeremy Goss – via Africa Geographic

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Image © Jeremy Goss– via Africa Geographic

Servals are listed on CITES II appendix, which prohibits international trade without a permit, and they are currently classified as least concern on the IUCN Red List. While they are not generally considered an endangered species they are suffering like all other of the wild cats.

The primary threats come from the bigger cats like leopards, dogs and most notably the ever-growing human population. Servals are poached for their beautiful coats, which are used for ceremonial and medicinal purposes, and even for their meat which is considered a delicacy by some African tribes. Fragmentation and loss of wetland habitat means loss of main prey sources like rodents, this in addition to the burning of grasslands, overgrazing by livestock and persecution by farmers, who consider them a threat to livestock, are also greatly contributing to their demise. Servals rarely take anything larger than a bird and do not pose a threat to humans but are often wrongly blamed for killing sheep and chickens.

Even though servals are not protected over most of their home range, hunting is prohibited in some of their range countries, there is no conservation plan in place but it is clear that any would be welcome to help better understand and ensure a future for this unique and elegant feline.