Cane Toad and Gulf Coast Toad co-inhabiting in the same burrowThe Deep South Texas terrain is quite interesting. It’s mostly a delta with none to very little elevation. Hence the features of the terrain are mostly thorn-scrub, at least what is still sort of intact. The rest has become ag-land for crops or urban sprawl. The point being that there are no rock cuts, or boulders or hills or other features that are conducive to providing herps a lot of hiding spaces. As a result they’re often found around people’s houses using artificial cover.

There was one incidence when I observed a Cane Toad and a Gulf Coast Toad co-inhabiting in the same burrow. It made me wonder why they’d do so if the Cane Toad could potentially poison the gulf coast toad or even eat it. I looked around the caliche pit and there weren’t very many hiding spaces, as is the case for most of the Lower Rio Grande Valley. So, my curiosity was overwhelming and I wanted to see who was being choosy about the burrow availability.

I collected 30 Cane Toads and 30 Gulf Coast toads. With the help of a NASA engineer we designed a box with identical burrows, except one was connected to a cooler and maintained a cool 75 degrees, while the rest of the chamber was brought up to 100°F, not unusual for the region. This caused the other burrows to maintain a temperature about 10-15 degrees lower than ambient temperature, but the cooled burrow remained at 75°F. We put in pairs of toads of the same species, or one of each species all for 10 minutes at a time, never using the same toad twice during one trial. We had infrared cameras set up to look inside the burrows and digital cams above recording their movements.

We found that Gulf Coast Toads will enter any hole they can inhabit to escape the heat, but Cane Toads, explored all available holes and 90% of the time chose the cool burrow. The other 10 percent of the time they chose burrows that already had a toad inside. We presented this work at the Joint Meeting for Ichthyologists and Herpetologists. The reason for this I believe is that by being in close proximity to another toad they reduce surface area and hence decrease desiccation. Another advantage is that if the “other” toad expels some water onto the substrate both the Cane Toad and the Gulf Coast toad can re-uptake it. Cane toads were sort of using the other toads as living canteens if you will, because they’re just bad-asses and excellent problem solvers.

Amplexed Gulf Coast ToadsIn evolutionary biology we always discuss animal’s basic needs and instinctual behaviors used to satisfy these needs. The Four F’s (fleeing, fighting, feeding, and well reproduction), are great drivers of some of the extreme or even awkward behaviors we sometimes see in nature. “Gotta do what you gotta do right?”

One day back in May of 2010 I was road cruising and a ton of rain had just fallen, the roads were thick with amphibians of all kinds. I drove down a dirt road on which both of the sides of the roads were flooded by ephemeral pools of water. The calls of Sheep Frogs (Hypopachus variolosus), Narrow-mouth Toads (Gastrophryne olivacea), Cane Toads (Rhinella marina), Couch’s Spadefoots (Scaphiopus couchii) and Gulf Coast Toads (Incilius nebulifer) among some were so loud the chorusing was deafening.

Shortly into my drive I found a very strange little scenario going on. Right next to the roadside ephemeral pool I noticed a pair of amplexed Gulf Coast Toads. Around the pair, like the scene out of some strange ritual, were 3-4 other male toads standing close by just watching, as if waiting for their turn. Well in fact, it turns out they probably were! They seemed to be acting out what would typically occur had they been just a few inches further in the actual water body. When a male and female amplex, satellite males sneak nearby trying to fertilize some of the eggs to pass on their own genetics. In this case they were just outside the water body.

However, what was the big deal with the deal female, how could that even work right? Well back in 2012 (Izzo et al. J. Nat. Hist. 46:47–48) observed similar behavior playing out. They termed it “functional necrophilia” in which even when the female is already dead, the male is able to massage the still viable eggs, out of her fresh body and fertilize them. Thereby, benefiting both individuals including the dead female, as her genes also get passed on along with his own.

The instinct of the fourth F, ‘reproduction,’ is a strong one. I guess one can relate, right? Nevertheless, we reported the first case of necrophilia in Incilius nebulifer in the journal Herpetological Review (2013, 44:4 pp. 655-656).

The force is strong with the four Fs! Of course since then (and prior to this publication) we’ve learned of necrophilia in lizards, snakes, other anurans, and it likely occurs in other taxa as well, and if we haven’t reported it, we’ll stumble upon it eventually. How successful the strategy is among other vertebrates is still a topic of discussion, but at least with some anurans we know it works!

As for the creepy satellite males standing by on watch, well, they’re just going to have to keep watching until the amplexed male works his magic massage!

Gulf Coast Ribbon Snake (Thamnophis proximus orarius) mating ball in January (winter) displaying stage III courtship behaviorm
In the previous blog we discussed how snakes’ breeding behavior is different in the Lower Rio Grande Valley (LRGV), and gave an example of the case of Leptodeira septentrionalis, Northern Cat-Eyed Snake, an attractive species unique to this region. Although the literature says they’re spring breeders, it seems that our field observations contradict that.

An even more drastic example of snakes that breed without brumating in the LRGV are Gulf Coast Ribbon Snakes (Thamnophis proximus orarius), they too, are supposed to breed during the spring. One day back in 2010 I was hiking through a small refuge and noticed a rather small mating ball consisting of about 8 snakes. This occurred in January, still winter, and the snakes were in full courtship behavior. Over the next few days I continued to observe them around the same “denning” site, which consisted only of a dense pile of branches. I documented this behavior and published it as the earliest reproducing snake in the country (Oyervides and Zaidan, 2014. Herp.Rev. 45(1):574). Over the course of the next few years I continued to monitor the behavior of this species in this region.

I’ve now learned that they breed year round. One would think that this would be detrimental to the snakes and they’d likely breed themselves to death in an effort to put out as many litters as possible, but it seems that’s not the case. Neonate and gravid Ribbon Snakes can be found year round in this region. In conducting my field surveys of these, I’ve also located a record size Ribbon snake, and one with a record size litter. Thus if they’re growing this large, having multiple litters per year doesn’t seem to be detrimental to them.

Their breeding behavior is also quite contrary to what the literature says, mind you, that last update on their biology was back in the 50’s by Tinkle. There is a very marked dimorphism between males and females of the species. When a female is being courted, she has several small males around her. These will follow her around and shadow her every move. Unlike in large mating balls where the males stress the females so much they practically force them into copulation, here, the female decides when she’s ready, as the males are too small to force her to do anything. These satellite males as I call them, will follow her around for days or weeks until she’s ready. Upon copulating, the males will disperse, and she will spend a lot more time up on tree branches absorbing as much sunshine as she can to speed up the process of having her first litter of the year and prepare for the next.
The advantage to this behavior is that because of the warm climate, there is a food supply for neonates year round. Moreover, their population numbers really decrease during years of drought. Having such a high number of individuals ensures that at least some will survive the droughts and restore a healthy population as soon as conditions improve. It’s amazing how sometimes we know so little of some of the most common species around!
Female with a male where the sexual dimorphism is evident.

Northern-Cat Eyed Snake Leptodeira septentrionalis
The southernmost region of the Lone Star State is a very interesting location. It harbors several unique species only found here, as this is their northernmost range from either Mexico or Central America. With its dry subtropical clime, most of the year is hot and winters are extremely mild. The vegetation (or what’s left of it), consists of some succulent plants that extend through the sandsheet, thornscrub forests and chaparral.

In over a decade that I’ve been conducting research here, I’ve noticed that for many species, winters aren’t cold enough and certainly not prolonged enough to result in any significant brumation period. A lack of brumation time, interestingly, may result is several species here reproducing year round or producing multiple clutches in a year (this is a neat discussion topic).
For example, one very attractive species found only in this part of the country is the Northern-Cat Eyed Snake (Leptodeira septentrionalis). Relatively little is known about their natural history in this part of their range. We currently have ongoing projects with the species to learn more about their secretive lifestyle.

One observation I’ve made so far is that there are active neonates in December and January, and gravid females in September. This suggests the species is either double clutching or are fall breeders instead of spring breeders as the literature denotes (at least in this part of their range). Even without extended brumation periods, it seems in some parts of their distribution their populations remain stable, while in others they are facing environmental pressure due to habitat loss. I’ve noticed the peak of their activity is during temperatures in the mid 60s to mid 70s. They are rear-fanged and will feed on anurans, lizards, other snakes, and even mice. Finding neonates that late, (or early), in the year, poses more questions than answers for me. I guess we still have a lot more to learn about this enigmatic species.