Frogs and toads have finally begun to emerge from their winter hibernation in central Texas. We’ve had a fair amount of rain lately, at least in Austin, though much less in several surrounding counties, including Bastrop, where we went toad-hunting last night. Wildflowers, particularly bluebonnets, have begun to bloom in profusion. Signs of a Texas spring are everywhere—it couldn’t be more welcome, given how dreary the drought-induced landscape has become. It has also been somewhat warmer the last few days, after a strangely cool March which unseemingly followed an unduly warm period that hardly deserved to be called winter. Conditions for anuran emergence and breeding can hardly be better than at present.
At the Stengl Biological Station last night, ranid frogs were plentiful. It was a warm humid cloudy evening but without rain. Stengl’s central pond contained a lot more water than when I visited it last month. But a few more showers will serve the pond well—it’s still less than half the normal size for drought-free years. Bluegill sunfish (Lepomis macrochirus)—and, very possibly, the hybrid Redear × Bluegill Sunfish (Lepomis microlophus × L. macrochiru), also known to occur here—were abundant in the pond, jumping around and playfully maintaining the pond surface in a constant state of vibration. But, unlike last month, frogs were competing with the fish for attention. A leopard frog (Rana sphenocephala) chorus erupted periodically, often drowning out all the other noise of the forest. This southern leopard frog has an odd unmusical call, somewhat like a chuckle, but more guttural, a trill that sometimes seems like a half-hearted bark. It is loud, even by anuran standards.
There were leopard frogs every few feet along the muddy bank of the pond, often cleverly camouflaged in their surroundings. A few skittish individuals leapt into the water at the slightest provocation. (We weren’t particularly provocative, of course. We nearly stepped on them much of the time, used excruciatingly bright flashlights, and periodically captured some of them—nothing really severe.) But most of these frogs seemed to be in a strange state of suspended animation, lethargic enough to be easily caught and studied. Some had to be seriously prodded to show any sign of life. It almost seemed as if their metabolism is yet to recover from its winter torpor. A few bullfrogs (Rana catesbeiana) could be heard in the background, though these weren’t equally amenable to being manhandled. They appeared to be juveniles, with voices still in training, and no match for the leopard frog chorus.
Leopard frogs were just as common in the creek along the boundary of the station. The creek is yet far from full, but the dirty pond fragments were teeming with aquatic life. Several fish species competed with a few tadpoles. And as usual, there was an inordinate number of beetles. We didn’t see any eggmasses, which was surprising given the presence of tadpoles. That will undoubtedly change in the next few weeks. These pond fragments are little-understood ecosystems. They are like ephemeral ponds insofar as they are fragments of aquatic habitat separated from each other for much of the year. But, unlike ephemeral ponds, they don’t dry up when they disappear; rather, they become part of a flowing creek. They are almost like freshwater tidal pools, except that they are renewed at odd inervals during the year, and not every day. An ongoing census of these pond fragments would be interesting, especially if it tracked changes of chemical composition.
There are at least ten anuran species at Stengl but we didn’t encounter even half of them last night. We heard Gray Treefrogs (Hyla versicolor) in the background—they had apparently been calling throughout the day, whenever the sun was obscured by clouds. We caught a single elegant Green Treefrog (Hyla cinerea) at the creek but there was no sign yet of breeding in this species, no eggmasses under the leaves. The creek area of Stengl is generally more lively than the rest of the station and less visited—an armadillo crashed through the undergrowth while we walked towards it. Orb spiders were everywhere, more prominent at night than during the day with the flashlights illuminating their bright eyes. Moths, though, were less common near the creek than near the pond.
As always, it was invigorating to be in a forest at night. But we were never in danger of thinking that we were in some remote untransformed landscape. Every few minutes, planes flew overhead on their way to the Austin Bergstrom International Airport (proudly “international” even though it doesn’t have a single scheduled foreign flight). The leopard frog chorus shut down whenever a plane approached. A helicopter also flew directly above us. But the leopard frog chorus didn’t deign to notice this minor disturbance. There was no point at which we could avoid the noise from the traffic on Highway 71. But we still managed to get lost in the dark, though only for a few minutes. Even fragments of unkempt forests are better than none.
Phil Schappert spotted a Gulf Coast Toad (Bufo valliceps) near his home at the edge of the station. Or should we say Coastal Plain Toad (Bufo nebulifer), now that molecular analysis has resulted in the traditional species being split into two with the older name reserved for the southern version (from Mexico to Costa Rica)? Or perhaps we have to go even further—some molecular biologists now claim that this fairly common toad doesn’t even belong to Bufo and deserves relegation to the somewhat more obscure genus, Cranopsis. (From Bufo valliceps to Cranopsis nebulifer in a few easy molecular steps—I’m sure there is a moral in this story somewhere.) In any case it was there, somewhat earlier in the year than expected.
But, of our main quarry last night, the endangered Houston Toad (Bufo houstonensis), we found not a single sign. Schappert apparently heard a few calling the two nights ago but the toads weren’t equally obliging after we arrived. The conditions were close to perfect for it to get into breeding mode though it probably prefers more moisture on the ground. Perhaps our mistake was to call of the search too early—we quit a little after ten-thirty. Our wait continues though there is every sign by now that this will be a bad year for the Houston Toad. Perhaps more rain will do the trick. But it already seems clear that this toad is more finicky than others, yet more reason (besides habitat transformation) to worry about its future.