Red wolves and grey wolves may have once been a single species. But throughout the 1900s, the interbreeding of coyotes and red wolves  blurred the line between species. How can we  determine whether red and grey wolves are the same or separate species?

The question is a pressing one, if you consider that conservation efforts are based on species.  In 1973, the Endangered Species Act was passed, creating the Endangered Species List, which mandates conservation efforts for every animal and plant on the list – based on species. Without a clear definition, conservationists don’t know what exactly they are trying to protect. The red wolf is on the list, but the more populous grey wolf is not. However, if the red wolf and grey wolf were considered the same species, the red wolf would be removed from the Endangered Species List and lose the protections and monetary assistance that the status of being listed provides.

First, a definition: a species is the fundamental biological grouping and denotes a group of the same organism that live, eat, and breed together. Species split frequently, whether through geographic separation, different populations beginning to eat different things, or hybridization (when one species mates with another) (Sites and Marshall, 2004). Hybridization blurs the species boundary. The dog and wolf in the photos below are difficult to tell apart just based on their faces and skulls. Sometimes, a face or skull is all we have.

Species definitions are nonetheless  important for conservation efforts. 

Fortunately, a more sophisticated version of the above skull-shape comparison can help define species by looking at quantifiable differences between skulls. This process is called geometric morphometrics. The shape of the cheekbone, or the curve of the top of the skull are some examples of the shapes that can be analyzed. These shapes are taken from 2D pictures, then plotted onto a graphCartesian coordinates. With many skulls, trends of each shape can be seen on this graph. If the shape of the cheekbone looks one way in grey wolves, a second way in red wolves, a third way in coyotes, and the red wolf-coyote hybrids look a fourth way, then these species are separate.

Maybe the species distinctions will be completely different from what we expect. There might not be a difference in the shapes, which in itself would be interesting. Or maybe the shapes will be a confusing blob, and a different method will be needed to figure out what is going on. Although genetics are complicated by the inbreeding, difficult with the inbreeding, they may be able to shed some light on differences between the groups.

There’s a question of whether the original wolves in North America were red wolves. This is a complicated question since red wolves interbred heavily with coyotes as their geographic range shrank. They used to live across the southeastern United States but have been reduced to a small region of North Carolina and the Louisiana-Texas border. Red wolves were declared extinct in the wild in 1980, when conservation efforts led to their being rounded up and moved  to a recovery area in North Carolina. They typically wear radio collars for tracking purposes. (Hinton, et al., 2013)

Luckily, there are skulls from red wolves before the interbreeding with the coyotes became routine, so geometric morphometrics can be done on red wolves, grey wolves, coyotes, and red wolf-coyote hybrids in the hope of defining each animal and figuring out if they are in danger of extinction.  Clarifying the distinctions between the four groups will solidify the species boundaries that inform conservation efforts. If all red wolves have a particular curve on their skulls that is not seen on (or is more pronounced than) any other skulls, that would be evidence that they are a separate group. Likewise, if grey wolves have a different curve that is distinct from what is seen on all of the non-grey wolf skulls, then grey wolves are a distinct group. If those differences are statistically significant, it is evidence that those groups are separate species. Knowing what (and how many) animals are in each species allows determination of extinction risk.

Conservation is a difficult field. There’s lots of contention among scientists about species definitions, best practices for helping different animals (as well as plants), and a general lack of funding. With constant advancements in science, conservation is always changing. As seen with the wolves, species definitions are also a source of headaches with much room for debate. Yet, most scientists want what is best for the animal to the best of our knowledge at that moment. And as that knowledge changes, our response will too.

Acknowledgements:

EAS-G 590 has allowed me to explore my thesis topic and amass background knowledge. Writing the first draft of this post was part of this class, as a part of practicing writing for different audiences.

References:

Hinton, Joseph W., Michael J. Chamberlain, and David R. Rabon. “Red wolf (Canis rufus) recovery: a review with suggestions for future research.” Animals 3.3 (2013): 722-744.

Sites Jr, Jack W., and Jonathon C. Marshall. “Operational criteria for delimiting species.” Annu. Rev. Ecol. Evol. Syst. 35 (2004): 199-227.

Edited by Evan Arnet and Liz Rosdeitcher