Wednesday, May 2, 2012

THE RINGED TAIL TALE

The Ring-tailed Lemur of Madagascar.
At our recent event, Exotic Species Night, visitors of all ages had the opportunity to see, touch, smell, and experience the museum's strangest, most exotic natural history artifacts. One booth in particular received a great deal of attention -- the "Odd Objects and Curious Artifacts" table. This table was a hands-on, touch-everything station with a collection of mystery "stuff" ranging from Mastodon teeth and whale earbones to Pencil Urchin spines and giant Tusk Snails. One object was particularly intriguing to some of our younger visitors -- a long, bushy, black-and-white striped tail. Nearly everyone correctly identified the original owner of the tail as none other than the Madagascan Ring-tailed Lemur. But one particularly inquisitive 4th-grader wasn't convinced.

"But couldn't it also be a raccoon's tail?" she asked. "Raccoons have striped tails too! How do you know it's  not a raccoon tail?" After reassuring her that I personally had seen the lemur before it became tail-less (which truthfully was not all that reassuring), I explained that raccoons typically have shorter, rounder, more bushy tails than Ring-tailed Lemurs. "Cacomistles and coatis on the other hand," I continued, "have tails that are quite similar in length and shape to a lemur's. They would be very hard to identify if I didn't know where they were from!"

And then came the big question.

"Why do they all look the same?"



The Ringtail, or Ring-tailed Cat, can be found
in the Southwestern United States. It has a
relative farther south known as the Cacomistle.
Both are not actually cats, but are more
closely related to raccoons and coatis.
Many species of coati, a Central and South American
relative of raccoons, also have ringed tails.
Raccoons are the best local representative with the ringed-
tail color pattern.
Without even knowing what a coati or cacomistle was, this curious ten-year-old girl knew that something interesting was going on here. In fact, this question has intrigued mammalogists and evolutionary biologists for nearly two centuries and we're still not entirely sure why so many animal tails have converged on this color pattern. Coatis, cacomistles, raccoons and Ring-tailed Lemurs aren't the only ones. This "ringed tail" business is far more widely distributed than you'd imagine. Excluding the bears (Ursidae) and the seals (Pinnipedia), more than half of the families in the order Carnivora have ringed tails. That includes things like the Red Panda, raccoons, cacomistles, coatis, and ring-tailed cats (not actually a cat), as well as civets, linsangs, genets, and most true cats like Tigers, Leopards and Cheetahs. Recent paleontological evidence suggests that even some dinosaurs had black-and-white striped tails!

Cheetahs have partially ringed tails used mostly for camouflage.
Clouded Leopards also have ringed tails.
The Tiger's ringed tail is probably used for camouflage too.
Sinosauropteryx was a the first dinosaur to show distinct color patterns
 in its fossil remains. Paleontologists believe that it had a ringed tail just
like many modern day mammals.

The Spotted Genet and many other
members of its family have ringed tails
which they use for communication.
In spite of this relatively high rate of ringed-tailed-ness in Carnivorans, evolutionary biologists believe that the first Carnivores probably had uniform tails. The fancy tail patternings most likely evolved later in arboreal, nocturnal species as a means to visually communicate with other animals at night (the contrasting bands are easy to see in darkness). But why only in arboreal species? How could a striped tail make you a better tree-climber? Well, it doesn't, but having a long tail does. Animals that live in the trees use their long tails for balance and support as they move along branches. These long tails are rather conspicuous -- sometimes they make up more than half of the animal's body-length -- the perfect place to put up a billboard! A long bushy tail is essentially a blank canvas on which an animal can place valuable visual cues and signs for other individuals. For most Carnivorans, these visual cues take the form of ringed tails.

There are, of course, some exceptions and odd balls. The Cheetah for example, has a partially striped tail despite it's very terrestrial lifestyle. As do Tigers. In some of these cases, terrestrial species have evolved a spotted or striped coat for camouflage, and these stripes/spots simply continue down the length of the tail. But according to the evolutionary biologists, most ringed tails evolved entirely independently from patterns on the rest of the body -- meaning ringed tails used for camouflage are the exception to the rule.

As for the ringed tail of the Ring-tailed Lemur (a Primate, not a Carnivore), the same rules probably apply. A long tail for arboreal locomotion is a great place to put some valuable visual cues regardless of whether you are nocturnal or not. We know that lemurs are very social, so it makes sense that they would utilize their tail to communicate. And Ring-tailed Lemurs do in fact use their beautiful tails for unique displays such as scent displays and aggressive interactions between rival individuals.

So, long story short, black-and-white striped tails are an excellent example of convergent evolution among relatively unrelated animal groups (raccoons to lemurs to dinosaurs) and are used for communication, especially in arboreal and/or nocturnal species. If you'd like more information regarding color patterns in the Carnivora order, check out Alessia Ortolani's scientific paper from 1998 titled "Spots, stripes, tail tips, and dark eyes: Predicting the function of carnivore color patterns using the comparative method." PDF here.

Stay curious!
-Robert Niese
Education and Outreach Coordinator

2 comments:

Anonymous said...

Great Article! We are learning about convergent evolution right now in Bio 112, so it was so fun to read an article that tied to the lesson! :)

Olivia S. said...

Very interesting! I never had put this much thought into the purpose of ringed tails, but now after learning about the social aspect of it, the purpose seems so clear!