The evolution of striped coat patterns in African mammals-what function do the stripes have?

Abstract

<p class="jbls"><span lang="EN-GB">Several families of mammals have stripes and many hypotheses have been proposed to explain the evolution of the striped coat patterns. However, there is very limited experimental evidence to support which hypotheses are the most likely to explain the evolution of the striped patterns. Therefore, what adaptive function the stripes serve in all these species is still largely unknown. In this study I investigated the characteristics of stripes such as stripe width for both white and black stripes on 36 striped African mammals’ coats collected in four museums and three countries. My study further revealed that the appearance of stripes on mammalian coats is most likely not involved in sexual selection. There were close similarities in stripes number or stripes width between sexes for <em>Equus grevyi</em> and <em>Tragelaphus</em> <em>imberbis</em>. In order to evaluate the effects of stripes on tabanids attractiveness, two experiments designed to test tabanids attraction were performed. Data on tabanids daily activity revealed that the flies were more active on partly cloudy and sunny weather. Especially, <em>Haematopota pluvialis</em> is known to have a high flight intensity in cloudy weather before an anticipated rain. Using sticky panels and models, tabanids were more attracted to sunny sides in the both experiments. Moreover, the findings revealed that the stripes in all striped patterns were extremely important in stimulating tabanid flies’ repellency. My results suggest that the appearance of stripes on different mammalian coats could be an evolutionary force reducing the attraction of tabanids to many striped animals, consequently, reducing disease transmission risk.</span></p>

Do the Stripes on Three-Dimensional Models Overcome the Odor Signals in Tabanids Landing Choice?

“…However, the black control model has signaled a significant difference not only between sunny and upper side but also between sunny and shady side in number of captured tabanids. The result was not surprising, as it has been experimentally demonstrated earlier that the capture rate of the tabanids was higher on the sunny side compared to the shady side of black patterns (Vaduva, 2016).…”

“…Observations that stripes themselves are visible from a distance of more than 20 meters compared to the polarization contrast between stripes, support the hypothesis that any striped pattern according to Vaduva (2016) is repellent to tabanids, for a totally independent reason of polarotaxis (Britten et al, 2016).…”

“…The results showed a strong repellency by tabanids in the same time with the introduction of stripes and least attraction to narrow zebra stripes. Simultaneously, other attraction experiment pointed out a significant repellency of tabanids by striped area of Okapi comparing with such great attractiveness to its homogenous black surface (Vaduva, 2016).…”

“…The number of stripes was the average number of stripes between Lesser Kudu and Great Kudu. In all 3D striped models, the chosen stripe widths pointed out the average for black and white stripes (for each part of body) from all specimens and also species within the same group (depending on stripe orientation) after the measurements in museums in three countries (Vaduva, 2016). All 3D models have been covered with Temmen insect glue, produced by TEMMEN GmbH Germany.…”

“…Apart from zebras, striped mammals are also found in some of the other mammal families such as Giraffidae and Bovidae. Carnivores also have a large number of different patterns including stripes, blotch, spots and so on (Vaduva, 2016).…”