Zebra Stripes: Fashionable and Evolutionarily Functional

In fashion there are black and white stripes, then there are zebra stripes! Immediately recognizable by their organic and wavy form, zebra stripes are a bold choice that can be paired with other prints or as a standalone statement piece. But, whose stripes are you really wearing? There are three zebra species: Plains (Equus quagga), Mountain (Equus zebra), and Grevy’s (Equus grevyi). The three species have differences greater than their stripes, particularly their conservation status.

Conservation of Zebras
The Plains zebra is currently listed as “Least Concern” by the IUCN Red List. In 2002, the population was estimated at over 650k individuals. Local populations of Plains zebras may decline from habitat loss and/or hunting; however, across the range the species has a stable population size. In contrast, the Mountain zebra is vulnerable and the Grevy’s zebra is endanger of extinction. Both the Mountain and Grevy’s zebras have small, local distributions that contracted as the environment changed from the Pleistocene to the Holocene (see this paper regarding Grevy’s range contraction). The Mountain zebra population has been increasing since 1998, and is currently around 1,500 individuals. The main threat to Mountain zebras is competition with livestock, including fencing which limits their access to watering holes. While the population size of Grevy’s zebra is similar to that of the Mountain zebra (~1,800 individuals), the population trend has been estimated at a greater than 50% decline since 1988. The main threat to Grevy’s zebra is livestock, where competition for food and water, reduction of high quality grassland due to overgrazing, and introduction of disease appear to limit juvenile survival to reproductive age.

Evolution of Stripes
There is a popular perception that zebra stripes help individuals in a herd avoid a predatory attack by confusing predators. Under this hypothesis, when zebras stand together, the stripes blend and make any individual animal appear larger, thus harder to take down. However, other hypotheses for the evolutionary purpose of zebra stripes have been proposed including: camouflage with background environment, as a regulator of body temperature, as kin recognition, or to avoid attacks from ectoparasites such as tsetse flies. Two recent papers compared stripe thickness and number across different body parts (including the face, neck, trunk, and legs) to climate and other explanatory variables.

Caro and colleagues (sub) identified ectoparasite resistance as the reason for zebra stripes. They relate their statistical models to field research that shows that tsetse flies and tabanids (both biting insects) do not prefer to land on striped models, potentially because the insects cannot distinguish the animal from the background!

However, the model of Larison and colleagues (sub) showed that the stripes aided cooling the animal. Specifically, Plains zebras in the northern portion of their range have wider stripes and the stripes cover their torso (as compared to a partial white underbelly). In this paper, two temperature related variables predicted stripe patterns across the range lending support to the hypothesis that the stripes help cool zebras by creating stripes of hotter and cooler temperatures, thereby creating more convection over the body. Empirical evidence using temperature guns observed that zebra body temperature is lower than other similarly sized ungulates.

What species are you wearing?
Zebra stripes vary between species. Zebra stripes are vertical on the torso but turn horizontal on the hindquarters; the shape and angle of this transition varies between the Plains and Mountain zebra, where the Plains zebra passes through diagonal stripes and the Mountain zebra has a sharper contrast. Both Plains and Mountain zebras have wide stripes where Grevy’s have thin stripes.

Torso and hindquarters of Plains, Mountain, and Grevy's zebras. Note that the shadow striping (the silver stripes) of the Plains zebra is a characteristic of populations in the middle of the range.
Torso and hindquarters of Plains, Mountain, and Grevy’s zebras. Note that the shadow striping (the silver stripes) of the Plains zebra is a characteristic of populations in the middle of the range.

It may be hard to identify the species of zebra print you are wearing since designers take many liberties with the pattern for dramatic effect. In the Ungaro skirt, the designer made the edges of the stripes rougher than they would appear in nature. This skirt evokes the spine of the animal in the way the print comes together at the front seem. Both the Ungaro skirt and Burberry Prorsum cape show how to wear zebra with a second print. If you want to try this, make the zebra print the bolder of the two prints. If that’s too much print for you, try pairing zebra print with a bright solid color. Alternatively, you can wear all zebra print as shown in the gorgeous Felder Felder ball gown.

Ungaro abstract zebra print skirt from Resort 2015 collection. Pulling off a bold look of pairing two prints together but in great proportion where zebra print has large shape and geometric print has a smaller shape. Photo: Courtesy of Emanuel Ungaro via Style.com
Ungaro abstract zebra print skirt from Resort 2015 collection. Pulling off a bold look of pairing two prints together but in great proportion where zebra print has large shape and geometric print has a smaller shape.
Photo: Courtesy of Emanuel Ungaro via Style.com
Burberry Prorsum Resort 2016 zebra print cape with fringe edging, almost like a zebra mane! This print has thick stripes similar to northern populations of the Plains zebra. Photo- Courtesy of Burberry Prorsum via Style.com
Burberry Prorsum Resort 2016 zebra print cape with fringe edging, almost like a zebra mane! This print has thick stripes similar to northern populations of the Plains zebra.
Photo- Courtesy of Burberry Prorsum via Style.com
Felder Felder zebra print silver ball gown from Fall 2015 Ready-To-Wear collection. The abstraction of this zebra print is due to both the broken stripes and number of bifurcating stripes. Photo- Kim Weston Arnold from Indigitalimages.com via Style.com
Felder Felder zebra print silver ball gown from Fall 2015 Ready-To-Wear collection.
The abstraction of this zebra print is due to both the broken stripes and number of bifurcating stripes.
Photo- Kim Weston Arnold from Indigitalimages.com via Style.com
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