A pair of wood frogs in captivity.

April 5.  

April 5, 2018

What I call the young bullfrog, about two and a half inches long, — though it has no yellow on throat. It has a bright-golden ring outside of the iris as far as I can see round it. Is this the case with the bullfrog? May it not be a young Rana fontinalis? No yellow to throat. I found it on the shore of the Clamshell Hill ditch. Can jump much better than the others, and easily gets out of the deep pan.

Those to whom I showed the two R. sylvatica could not believe that they were one species, but this morning, on taking them out of the water to examine minutely, they changed so rapidly, chameleon-like, that I could only describe their first appearance from memory. The male grew a lighter brown and the female darker, till in ten minutes there was but a slight shade of difference, and their whole aspect, but especially that of the male, seemed altered also, so that it was not easy to distinguish them. Yet they would readily be recognized for rather dark-colored wood frogs, the posterior extremities of both having distinct dark bars. 

The female was two and one tenth inches long, the male one and four fifths inches long. The female was (apparently involuntarily) dropping a little spawn in the pan this morning, and the black core was as big as the head of a pin when it issued from the body. The only difference in color that I now noticed, except that the male was a shade the darkest (both a pale brown), was that there was a very distinct dark mark on the front side at the base of the anterior extremities of the female, while there was but the slightest trace of it in the male. 

Also the female was more green on the flanks and abdomen; also she had some dusky spots beneath. What is described as a yellow line along the lower edge of the dark one through the eyes, i.e. along the upper jaw, and which I observed to be such last spring, was in both these at all times a broad silvery or bright cream-colored line. 

Putting them into the water, after an hour they again acquired distinct colors, but not quite so distinct at first. It is singular that at the breeding-season, at least, though both are immersed in water, they are of a totally different color, -- the male a very dark brown for a frog, darker than the ordinary color of any Massachusetts frog, without distinct bars to his posterior extremities or a distinct dark line along the snout, while the female is a light reddish brown or lively dead-leaf color, — and that, taken out of water, they rapidly approximate each other till there is only a shade of difference if any. 

At their breeding-season, then, the colors of the male are not livelier, as in the case of birds, but darker and more sombre. 

Considering how few of these or of the R. halecina you meet with in the summer, it is surprising how many are now collected in the pools and meadows. The woods resound with the one, and the meadows day and night with the other, so that it amounts to a general awakening of the pools and meadows. 

I hear this morning the seringo sparrow. 

In the proceedings of the Natural History Society for December, 1856, there were presented by Dr. H. R. Storer, “a globular concretion of grass said to have been formed by the action of waves upon the seashore.” Were not these some obtained by the Hoars or Emersons from Flint's Pond?

P. M. – I go to the meadow at the mouth of the Mill Brook to find the spawn of the R. halecina. 

They are croaking and coupling there by thousands, as before, though there is a raw east wind to-day. I see them coupled merely, in a few instances, but no such balls or masses of them about one female as in the case of the R. sylvatica, though this may occur. 

You can easily get close to them and catch them by wading. The first lagoon within the meadow was not a foot deep anywhere, and I found the spawn where it was about eight inches deep, with a grassy and mossy bottom. It was principally in two collections, which were near together and each about a yard in diameter. The separate masses of this were from two to six, or commonly three or four, inches in diameter, and generally looked quite black and dense or fine-egged in the water. But it really on a closer inspection presented quite an interesting variety of appearances. 

The black core is about the size of a pin-head, and one half of it is white. It commonly lies with the black side up, and when you look directly down on it, has a rich, very dark blue-purple appearance. When with the white or wrong side up, it looks like a mass of small silvery points or bubbles, and you do not notice the jelly. But it lies also at all intermediate angles, and so presents a variety of appearances. 

It is attached pretty firmly to the grass and rises just to the surface. There are very fine froth-like bubbles more or less mingled with it. I am not sure that I can distinguish it from that of the R. sylvatica. 

I caught several of the first. The dark blotches on the back were generally more or less roundish with a crenate edge. There were distinct, raised, light bronze colored ridges from the snout along the side-head and body, which were conspicuous at a distance. They were, all that I caught, distinctly yellow-white beneath, and some had green buttocks. 

And now, standing over them, I saw that there were considerable lateral  bubbles formed when they croaked, i. e., the throat was puffed out on each side quite far behind the snout. The tympanum was very convex and prominent. 

At evening I find that the male R. sylvatica couples with or fastens himself to the back of the young bull frog (?)*, or whatever it is, and the latter meanwhile croaks, in short croaks four or five times repeated, much like the R. sylvatica, methinks. 

I hear the hylodes peeping now at evening, being at home, though I have not chanced to hear any during the day. They prefer the evening.

H. D. Thoreau, Journal, April 5, 1858

Rana halecina (Lithobates pipiens)  – Northern Leopard Frog. See April 5, 1857 (“I hear the croaking frogs at 9.30 P. M.”); and note to April 3, 1858(“the Day of the Snoring Frogs, or the Awakening of the Meadows.”)

The black core is about the size of a pin-head, and one half of it is white. See April 4, 1857 ("Caught a croaking frog . . .. Nearby was its spawn, in very handsome spherical masses of transparent jelly. . . consisting of globules. . . with a black or dark centre as big as a large shot."); April 4, 1858 ("There was a good deal of spawn firmly attached to the brush close to the surface, and, as usual, in some lights you could not see the jelly, only the core.")

 I hear the hylodes peeping now at evening,  though I have not chanced to hear any during the day. See note to April 5, 1854 ("Hark! while I write down this field note, the shrill peep of the hylodes is borne to me from afar through the woods"); See also April 1, 1860 ("I hear the first hylodes by chance, but no doubt they have been heard some time.")

*According to Maine Department of Inland Fisheries and Wildlife male wood frogs search for a mate by hugging other frogs until they find one who is round enough to be carrying eggs.