Catching Xenopus in Baja California, Mexico

With the invasive population of African clawed frogs being in so many drainages in San Diego, it was long expected that they would cross the border into Tijuana, the city at the border between USA and Mexico. But it wasn't until 2014 that Anny Peralta-García and colleagues reported that these frogs had not only crossed the border, but had travelled around 20 km South along the coast and appeared to have moved up the drainage inland.

The Tijuana River does not look hospitable to African clawed frogs, but when the flow is slow like this, they can use it as a corridor to expand their invasion.

Reports from Anny and colleagues with those posted on iNaturalist now indicate that the invasion has moved ~40 km south of the border. I was very lucky to be able to work with Anny and Jorge and make a quick visit to Baja-California. Both Anny and Jorge were out of town, but I met up with Diego Maldonado who very kindly picked me up in Tijuana and drove me to the two southernmost sites to place traps.

Diego at one of the sites near Puerto Nuevo.

Although we were unlucky at the inland site, we found large numbers of animals near Puerto Nuevo. Here you see Diego pulling in one of the traps.

Moreover, we could see many animals in the water. I've ringed a couple in the picture below. How many more can you see?

Thanks to Anny, Jorge and Diego for making my trip to Mexico not only possible but also successful. It was great to learn about Baja-California and see some of the beautiful areas that Xenopus has invaded.

Literature

Anny Peralta-García, Jorge H. Valdez-Villavicencio, and Patricia Galina-Tessaro "African clawed frog (Xenopus laevis) in Baja California: a confirmed population and possible ongoing invasion in Mexican watersheds," The Southwestern Naturalist 59(3), 431-434

Xenopus from LA with stars in their eyes

Among all the glitz and glam of life in LA, there is an invasion of African clawed frogs that has made its way into many of the waterways and drainages in the area. I was very lucky to meet up with Greg Pauly from the LA County Museum. Greg has his own passion for Xenopus with a citizen science project to determine how diverse their predators are (see here). Greg is a fountain of knowledge about all things wild and urban in LA, so of course he was the perfect guide for collecting clawed frogs. Greg knew of many sites to catch frogs in LA, and was happy to get his seine net out and hit some of LA's most salubrious spots to pull some specimens out of the water. 

Greg took us to two sites in the LA area. The first (pictured above) was inside a park where Greg had seined animals before. We were joined for the day by Estella and Taylor from the LA County Museum who were both great frog wranglers once we got the seine net in.

We collected a bunch of tadpoles and ~10 adults from this small pond connected to the road sewer system. The water was really fowl and black. The frogs and tadpoles seemed to love it!

After we got over the stench of our equipment at the first site, we were quite unprepared to find something much much worse. The second site was really bad. Above you can see how it looked after we had finished seining out the many plastic bags, condoms, masks and other unidentified matter from this road sewer. Note the grey-brown colour of the water - for those not in the know, this is the colour of raw sewage. Once again, we caught a bunch of tadpoles and around 20 adults from this site. They appeared not to share our concerns about the water they lived in and instead appeared to be thriving there, and it was even possible to see the stars in their eyes...

Thanks so much to Greg, Estella and Taylor for making this trip to LA so successful!

An unexpected meet up with David Bickford

While travelling in California conducting fieldwork on Xenopus, I was contacted by David Bickford with respect to a chapter that we have been working on for what seems like a very long time. I remembered that David worked in the LA area, and so I reached out to him to meet up. In the pic below, David is showing off all of his Mandica memorabilia. He and Mark were lab mates for a while in Miami.

As David was about to move house, he had plenty of space and so I stayed a few nights with him and side-kick Datsie. Anyone who knows David will know that it was great fun to spend time with him, and we found time to drop traps at some of the best places that LA has to offer. Here are some of the highlights:

Trapping at a known site in Corona, Orange County. We didn't catch any Xenopus, but we did meet some interesting characters who hang out under the bridge. 

Another fun hang-out in the Jurupa Valley near Riverside. No appropriate trapping places here, but David shows us how he can make his lower half disappear.

Although David and I had no success in Orange County, I hope that there maybe a sample to come from there in future. There are certainly enough dodgy spots for our Xenopus to hang out in.

The lush and leafy suburbs of Washington are invaded

Unlike the dry canyons of San Diego, Washington State is a very green place with endless forests of trees, and plenty of water cursing through creeks out to the sea. In 2015, the first records of African clawed frogs started coming in from a stormwater pond in Bothell, WA. Two boys were fishing and saw an unusual looking frog moving in the water. The same year, in another stormwater pond in Lacey, WA more Xenopus  were found. The two invasions appear unrelated other than a change in the legislation at the time that advised people that anyone keeping these (and other) potentially invasive animals as pets would require a special permit and meet biosecurity conditions. The result seems to be that the animals were dumped and the invasion started. By 2019, another site (Issaquah, WA) to the south of Bothell was found to be teaming with Xenopus. Another invasion, or animals travelling through creeks and lakes? 

  I've been in contact with the good people of DFW Washington State since the start and we have had many email exchanges and discussions about how best to tackle these invasions. However, the area is full of stormwater ponds and creeks that connect them, so appears ripe for continued invasion. 

I was given lots of help in Washington by Reed Ojala-Barbour (Jen and Al) who came to show me all the sites. Max Lambert was also hugely helpful, traffic delays aside, we had a successful day out in Issaquah. Other helpers in Lacey were Megan Friesen and Mark from Saint Martin’s University (Lacey) who kindly allowed me to use their lab space.  

One of the really special treats for me was to see Xenopus laevis in the same traps as Ambystoma gracilis. These two species would never naturally meet, but have some interesting similarities.

Further Reading: 

Field work to catch African Clawed frogs in San Diego

San Diego has the world's oldest extant invasive population of African clawed frogs, Xenopus laevis. I visited briefly in the summer of 1995 when I was doing my PhD studies, and successfully trapped in Tecolote Canyon and a pond in Spring Valley (Avocado) where I captured large numbers of individuals. 

The creeks in the San Diego canyons yielded large numbers of X. laevis  on this trip.

It was also great to revisit Tecolote Canyon with Alina and Tyrone who have been working there for the past 15 years or so. Now looking much better than it did in the 1990s, Tecolote Canyon is home to a thriving population of African clawed frogs. 

Thanks so much to Carla, Tyrone, Alina, Olivia and Lin for all their help in making this trip such a success.