While small inconsistencies in the appearance of wild animals is normal, every now and then nature rolls out unique and sometimes rare deviations from the norm. In 2020, two dwarf giraffes were identified from geographically isolated locations, and just recently a seal colony in England saw several melanistic seals among the pupping season’s winter baby boom. Plains zebras are famous for their stripes (we even have crossings named after them in England), but they too are known to sometimes practice some artistic license, phenotypically speaking.
Research published in the journal Molecular Ecology discusses the significance of these alternative coat combinations and what it means for the health of the species. Zebras have enjoyed relatively stable population numbers historically, but even so the global population is thought to have diminished by around a quarter since 2002. Study author Brenda Larison and colleagues fear the instance of unusual spotted or blonde zebras could be an indicator of diminishing genetic health among the animals.
Genetic diversity is vital within most species, and the catastrophic health effects of diminishing the gene pool through inbreeding or selective breeding has been demonstrated both in captive tigers and breed-associated health problems in domestic dogs. In the wild, a healthy environment would see genes flowing freely through populations, ensuring the health of offspring and the survival of the species.
This gene flow can be disrupted by anthropogenic (human) interferences, such as destroying habitats for agriculture and establishing towns and cities. To assess the gene flow of plains zebras, Larison and her team sequenced the genes of 140 animals who were distributed across nine locations. Seven of those included in the study had abnormal stripe patterns while the rest sported the typical black-and-white striped coat.
The analyses showed that while genetic structure didn’t not coincide with coat variation within a specific subspecies, it did identify where gene flow was limited as the result of habitat fragmentation. Animals from these populations presented with evidence of inbreeding. Furthermore, the animals tested who had unusual coats showed increased evidence of inbreeding compared to animals with conventional zebra stripes within their respective populations. “Our results point to a genetic cause of stripe pattern abnormalities, and dramatic evidence of the consequences of habitat fragmentation,” concluded the study authors.
While variations in coat patterns may not directly negatively impact the health of these animals, standing out from the crowd can be problematic for wild animals in hindering their chances of being selected as a mate. Sexual selection favors animals with the “healthiest” coats, and changes to the zebra blueprint may be interpreted as a sign of dodgy genes. Furthermore, animal patterns are often an adaptation to their specific environment, sometimes as a means of breaking up their silhouette so they’re less visible to predators or a clever way of making it difficult for parasites to land on skin. Animals who veer from the norm could therefore be something of a square peg in a round hole if their fresh new look isn’t fit for their environment.
[H/T: National Geographic]