Stumbling Upon an “Extinct” Rodent on the Edge

A rat may not sound like an animal worth caring about. But, the San Quentin kangaroo rat (Dipodomys gravipes) is not your ordinary rodent. Kangaroo rats get around by jumping on their two hind legs like miniature, pouch-less kangaroos.

One of the 22 species of kangaroo rat, the San Quentin kangaroo rat exists only in a sliver of desert landscape in Baja California, Mexico. It has a larger body than other kangaroo rats in the area and a long, tufted tail.

When Dr. Laurence Huey first discovered this species in 1925, it was abundant. He found as many as 1,000 in just 10 acres of land. However, their range was never huge—as small as 150 km long and a few kilometers wide. Back then, the town of San Quentin didn’t have a paved road and farming in the area was minimal. That small range was just big enough for these kangaroo rats to thrive.

Paved Over and Pushed to the Edge

But, everything changed in 1973. The road running through the San Quentin kangaroo rat’s habitat was paved, and big agriculture moved in. The landscape changed from open desert grasses to endless fields of irrigated strawberry and tomato plants.

By 1980, scientists were only able to find two individuals. Several surveys were conducted throughout the 1990’s, but not even one was found. According to the Mexican government, the San Quentin kangaroo rat was officially considered extinct in 1994, although it hadn’t been seen since 1986.

But, was it really gone?

Enter Dr. Scott Tremor and Dr. Sula Vanderplank. Scott is especially skilled at capturing and handling mammals, and Sula is an expert on the ecology of Baja California. Over the last 15 years, they and their colleagues at the San Diego Natural History Museum have been documenting the mammals living in the San Diego region.

Their mission seems simple. They want to find out what animals exist in the area and how many of each species there are. They have spent countless hours surveying with live traps to meticulously document the region’s animals. They are not picky about which animals and habitats they survey. They are looking for the extremely rare, the very common, and everything in between.

When it comes to the extinction of species, Scott has his doubts. He notes, “Whenever somebody says an animal is gone, I doubt it, or at least question it. I try to find out if there are surveys, and we go to the area and try to document it.”

Scott and Sula had questions about San Quentin. Agriculture had boomed there for years, but many farms were abandoned decades ago. The groundwater turned saline from the nearby saltwater, so San Quentin was no longer prime agricultural real estate. But, what was left of the land? Was anything left of the species that once thrived there? Scott and Sula went to find out.  

On the evening of July 4, 2017, they dropped live traps in degraded farmland near San Quentin. Early the next morning, they retrieved the traps. Describing the moment, Scott exclaims, “Lo and behold, there it was, in some really bad habitat! It was in a highly disturbed area on the edge of agriculture. And it was plentiful!” We “just happened to find it by accident,” stated Dr. Tremor. They were surveying land at the very edge of unfertile fields, only fifty feet from hills deemed unfit for agriculture.

But was this the “extinct” San Quentin kangaroo rat?

There is another species of kangaroo rat in this area, the Dulzura kangaroo rat (Dipodomys simulans). So, which species was it? Scott’s mammal handling skills came in handy, because the four trapped kangaroo rats were quite feisty. The team measured the animals, recorded their behavior, and compared the data to Dr. Huey’s 1925 field notes. It was undeniable. At almost twice the size of the Dulzura species, this was definitely the San Quentin kangaroo rat, not seen for over 30 years!

No time to waste

Now that they knew the species remained, they had to do something fast. They joined Jorge Andred and Enrique Alfaro from the local conservation organization Terra Peninsular to search for more of the species in nearby reserves. Jorge explains, “Right now, we are facing big threats in this area because these abandoned agricultural fields are about to be used again.” The recent arrival of desalination plants is paving the way for big agriculture to return. The San Quentin kangaroo rat avoided extinction once by finding small edge habitats. If the scientists could find them in reserves, they could protect their habitat and these rats would have room to leap once again.

Luckily, they found several San Quentin kangaroo rats in two natural reserves. Jorge is relieved, “It’s going to be protected for many years if not forever. To find it in natural areas has given us the opportunity to buy more land and protect more land. It is very important for us. We are in the planning stages to translocate the species to protected areas. It’s a good option for this species.”

The resilience of species and the power of partnerships

Its habitat was paved over, then heavily degraded by agriculture. But, the San Quentin kangaroo rat found a way to live in small edge habitats. This gives Scott Tremor hope. He says, “It’s easy to give up, and it’s easy to believe when other people say something is gone. But the reality is that a lot of species have great resilience and they can persist over time in small edge habitats. With slight changes, they can flourish.” And for the San Quentin kangaroo rat, it certainly helps to have a team of dedicated scientists by your side.

References

• Best, T. and Lackey, J. (1985). Dipodomys gravipes. Mammalian Species, (236), pp. 1–4.
• Fessenden, Marissa. (2018). This Kangaroo Rat Was Just Spotted For the First Time in 30 years.
• Huey, L. (1925). Two new kangaroo rats of the genus Dipodomys from Lower California. Procedures of the Biological Society of Washington, 38, 83–84.
• Tremor, S., Vanderplank, S., & Mellink, E. (2019). The San Quintín Kangaroo Rat is Not Extinct. Bulletin, Southern California Academy of Sciences, 118(1), 71-75.
• Vanderplank, S., Ezcurra, E., Delgadillo, J., Felger, R., & McDade, L. A. (2014). Conservation challenges in a threatened hotspot: agriculture and plant biodiversity losses in Baja California, Mexico. Biodiversity and Conservation, 23(9), 2173-2182.