Mother giraffes pass down some spot patterns to their babies, according to a new study.
The study also shows those patterns may offer protection from predators. The findings confirm a 49-year-old hypothesis about the inheritance of giraffe spots and highlight a new toolset that researchers can use to study the markings of wild animals.
“Giraffe spot patterns are complex and can be quite different among individuals, but we don’t really know their purpose in the wild,” says Derek E. Lee, associate research professor at Penn State and first author of the paper, which appears in PeerJ.
“Complex markings can help animals evade predators, regulate their temperature, or recognize family or individuals, all of which can affect their ability to survive and reproduce. In this study, we analyzed survival records and photos of spots of Masai giraffes, and show that spot patterns do affect juvenile survival and are heritable—they are passed from mom to baby,” Lee says.
Giraffe skin color is uniformly dark gray, but their spots are highly variable in color and shape, ranging from nearly round with very smooth edges to elliptical with jagged or lobed edges. Spot patterns do not change as an animal ages, which allows researchers to identify individuals based on their unique patterns.
Newborn giraffes with larger spots and irregularly shaped spots have better chances of survival during the first few months of life, the study shows. This increased survival could reflect better camouflage of these young giraffes, but it also could be related to other survival-enhancing factors, such as temperature regulation or visual communication.
Further, the study shows that in two of 11 spot traits researchers measured, circularity—how close the spot is to a perfect circle—and solidity—how smooth and complete the edges are—were significantly similar in mothers and calves. This suggests that the calf inherits these traits.
“Dr. Anne Innis Dagg, the first giraffe field researcher in Africa, presented evidence in 1968 that the shape, number, area, and color of spots in giraffe coat patterns may be heritable, but her analysis came from a small zoo population,” says coauthor Monica Bond, graduate student in evolutionary biology and environmental studies at the University of Zürich. “We used wild giraffes and modern imaging and analysis techniques to confirm her conclusions.”
This study also highlights how researchers can use modern image software and statistical methods to reliably analyze complex coat patterns.
“My hope is that other scientists will use the same tools to measure mammal coat patterns to advance our understanding of what these patterns mean,” Lee says. “Quantifying heritability and fitness consequences of variation in coat patterns could help us understand how and why complex coat patterns evolve in wild animals.”
The Sacramento Zoological Society, Columbus Zoo and Aquarium, Tulsa Zoo, Tierpark Berlin, the Living Desert Zoo and Gardens, Cincinnati Zoo and Botanical Gardens, and Save the Giraffes funded the work.
Source: Penn State