Frog and salamander tadpoles develop in July

July is a month of early harvest in the garden. Much of the produce; especially the greens, that have been growing through the long days of June can now be gathered. This is also seen with the berries. Wild strawberries, so common now, set the ri...

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A Blue-Spotted Salamander tadpole; note the gills behind the head and the four legs. (Photo by Larry Weber)

July is a month of early harvest in the garden. Much of the produce; especially the greens, that have been growing through the long days of June can now be gathered. This is also seen with the berries. Wild strawberries, so common now, set the ripening pace in late June. This is rapidly continued with the domestic strawberries and it may be hard for us to think of the first half of July without expounding on these bright red juicy berries. The small tree, elderberry, comes of age at about the same time. These tiny arboreal red berries never seem to last long where there are hungry birds in the area. Looking around, we'll also see ripening of blueberries, juneberries and raspberries beginning now. Each of these berries and fruits are the carriers of seeds and the plant uses good tastes, bright colors and large numbers to attract animals to disperse the seeds through ingestion. (Another example of plants making use of animals) But there are seeds of other types here too. During the second half of June, it was hard to not notice the orange and yellow hawkweeds in the roadsides and fields. Visiting the same sites now, we are sure to find clusters of seeds on "parachute-like" growths like that of the dandelion. These seed get their dispersal in the wind.

July is a time of fledgling birds becoming young adults. Other families are active too and young squirrels, chipmunks and rabbits scamper about in woods and in our yards. Butterflies and dragonflies that developed in the spring continue to flutter by while the growing grasshoppers, crickets and katydids hop their way to adults as well. Spider webs that have been present along the roads and grasslands now are larger; as are the web-makers, and they are more numerous. And plenty more is happening on these hot days of July.

It is during the second half of this month that the tadpoles that have been developing in the fast-shrinking vernal ponds reach their next phase and step out on land. It was way back in April that the chorus frogs, wood frogs and spring peepers began their breeding season in these same ponds. They were subsequently joined by leopard frogs and toads, mostly in May. They need a quick metamorphosis: made faster by the fact that their aquatic homes were getting smaller, almost non-existent, as we get to July. Feeding on algae, they grow fast. The tadpoles grow hind legs; later to be strengthened by front legs, and internally, they go from breathing with gills to lungs. By about mid July, they are ready to make that huge transition onto a terrestrial existence. Anyone walking in the wetlands in these next few weeks will encounter a plethora of tiny frogs and toads as they hop to a life on land. Less than an inch long, many will not survive this dangerous journey and adjustment to the new phase.

Not long ago in July, I took a trip that included visiting the shores of Lake Superior. Like many other observers of nature, I walked out on the large rocky expanses going down to this massive lake. These sites are a setting for plants and animals maybe not seen elsewhere. As I walked among the butterworts, white goldenrods and ninebark, I found plenty of pools between the rocks. Formed both by rainfall and spray from the lake, the water tends to linger here. I paused to look into these aquatic spots. I noticed movement and taking a closer look, I saw tadpoles swimming or gathering on the bottom to feed. I could tell from the large head, long tail and small hind legs that I was seeing frog tadpoles. From their size, I concluded that they were chorus frogs. They are easy to hear in spring, but not seen much later. I continued to look, hoping to find more, maybe some with front legs. I did not see any frog tadpoles with front legs, but here in the water, I did see tadpoles of another type that did have four legs. These also had a growth of gills behind their head; I was seeing salamander tadpoles. They were a little bigger than the frog tadpoles. Subsequent investigations told me that these were the tadpoles of our most common salamander: the blue-spotted salamander.

These salamanders, like frogs and toads, are amphibians and like their hopping cousins, they need to spend their first weeks in water, breathing with gills. Unlike the anurans, salamanders hatch with four legs and external gills. And so, it can be quite easy to tell the difference between tadpoles of salamanders from those of frogs and toads. Life in these pools for all the tadpoles is temporary and they will all mature to terrestrial adults. The blue-spotted salamanders are largely black with bluish splotches on the sides and grow two to four inches long. As adults on land, they are not seen often; living a cryptic existence usually under logs and rocks, coming out in rains. Like the chorus frogs, breeding is done in small ponds in spring; but the salamanders remain silent. It is only occasionally that we see their tadpoles as I did in these lake shore pools.


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A Chorus Frog tadpole (two legs) with a Blue-Spotted Salamander tadpole (four legs).(Photo by Larry Weber)

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