Male Gray Treefrog Ardor Grows When Female Is In Sight
The peak of Gray Treefrog courtship and breeding occurs in another month, but males are already actively calling near bodies of water. Frogs are highly sensitive to motion so visual cues play an important part in their courtship.
Male Gray Treefrogs are significantly more likely to give their musical, bird-like courtship calls when they are able to see an approaching female, and their calls are longer if females are nearby and within sight. This is a good thing, as research has found that female Gray Treefrogs choose mates on the basis of advertisement calls and prefer long calls to short calls. (To hear a Gray Treefrog calling, go to https://musicofnature.com/calls-of-frogs-and-toads-of-the-northeast/, scroll down to “Gray Treefrog” and click on arrow. Spring Peepers and Green Frog in background.)
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Bullfrogs Establishing Territories
The low humming sound of hundreds of male Bullfrogs “jug-o-rumming” on their breeding grounds fills the air this time of year. So energized are these frogs that singing occurs during the day time as well as at night.
While attracting a mate is one reason for this serenade, establishing a territory is the initial objective. According to Tom Tyning (Stokes Guide To Amphibians and Reptiles) a male Bullfrog’s territory is a circular area that may be anywhere from six to twenty feet in diameter. Males who are singing have established territories and tend to be the largest and oldest individuals. Should another male challenge a resident Bullfrog, there can be physical altercations in the form of wrestling matches in which males hold each other and attempt to gouge each other with their thumbs.
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Male Wood Frogs Calling
Usually it’s your ears that tell you that Wood Frogs (Lithobates sylvaticus) have emerged from hibernation. They are one of the first amphibians to announce themselves, often appearing before snow and ice are completely gone. Male frogs congregate in shallow ponds and vernal pools, where their ardent courtship ensues.
Unlike most frogs, which have a single vocal sac below their mouth, Wood Frogs have two paired sacs, called paired lateral vocal sacs, located on either side of their body just behind their head (see photo). With their mouth and nostrils are closed, male frogs pump air back and forth from their lungs to their inflated vocal sacs which vibrates their larynx and produces a duck-like quacking sound. The vocal sacs act as resonating chambers, amplifying the frogs’ calls so as to attract females from far and wide.
Vocal sacs serve a dual purpose for some frogs. As soon as the eggs of Darwin’s Frog (Rhinoderma darwinii), found in Chile and Argentina, hatch, the male scoops the tadpoles into his mouth and they spend the next six weeks metamorphosing inside his vocal sac. The male does not eat until the tadpoles have matured into adults and exited his mouth.
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Spring Peepers Peeping
The peeps of male Spring Peepers can be heard fairly consistently this time of year. Unlike in the spring, these calls are coming not from bodies of water, but from the woods nearby. And they are single peeps coming from individual peepers, not the chorus of “sleigh bells” one hears in the spring. This phenomenon occurs so regularly in the fall that herpetologists have given it a name – “fall echo.” They speculate that the calling of peepers is spurred by light and temperature conditions that mimic those that occur in the spring, during Spring Peeper mating season.
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Eastern Gray Treefrog
Congratulations to Naturally Curious readers for their familiarity with Eastern Gray Treefrog (Hyla versicolor) toe pads! This is the easiest time of year to find these amphibians, mainly because of their habits. During the fall, winter and spring treefrogs are usually silent, unlike the summer, when males can be heard calling their melodic trill from bushes and trees near bodies of water after the evening air temperature rises above 59°F. Because they are nocturnal, well camouflaged, and hibernate in the winter, you don’t often come across one except for the warmer months when males are calling. The colors of an Eastern Gray Treefrog (brown, green and pearl-gray) vary with the colors of its background and environmental factors such as season and humidity, but shades of gray are most common. Their green color is more prominent during the breeding season and in young frogs.
When hunting insects, or when disturbed, treefrogs can leap great distances and, thanks to advanced toe pads, when they land they can cling to practically any surface, including vertical branches and leaves that are wet. A very low angle between the toe pads and substrate as well as mucous glands located in channels between the hexagonal pattern on a treefrog’s toe pads have inspired the design for treads on car tires.
You can listen to an Eastern Gray Treefrog’s call by going to http://langelliott.com/calls-of-frogs-and-toads-of-the-northeast/ (Sound recording © Lang Elliott – langelliott.com)
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Green Frogs Mating & Laying Eggs
The loose banjo string call of the Green Frog is a familiar sound near wetlands this time of year. Males (to the right in photo, with bright yellow throat) have been busy serenading females (to the left in photo, with white throat), in an attempt to breed with one. Female Green Frogs select their mate, a choice which is based partially on the suitability of the male’s territory (underwater plants are a plus). After inspecting several males’ territories at night, the female chooses one and slowly approaches him, turning to face away from him as their bodies come in contact. External fertilization takes place as he clasps her while she lays her eggs (known as “amplexus”).
Unlike Wood Frog eggs that are laid in clumps, or Spring Peepers’ individually-laid eggs, Green Frog eggs are laid in a loose cluster that often floats on the water’s surface (see photo) or is draped on underwater plants. Each cluster usually consists of 1,000 to 5,000 eggs that hatch in three to five days. Females sometimes return to breed a second time with a different mate, in which case the second egg clutch is usually smaller, consisting of about 1,000 to 1,500 eggs.
The larval, or tadpole, stage of a Green Frog lasts from 3 to 22 months, which explains why you might have already seen large Green Frog tadpoles this summer.
(Outstanding theories were submitted on yesterday’s mystery. Be sure to read comments!)
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Male Pickerel Frogs Snoring
Next to the Green Frog, the Pickerel Frog is the most abundant frog in New England. It is often confused with the Northern Leopard Frog, which it closely resembles. The spots on a Pickerel Frog’s back are squarish and aligned in rows, whereas the Leopard Frog’s spots are rounded, and randomly scattered over its back. In addition, the male Pickerel Frog has bright orange on the inner surface of its hind legs, which the Leopard Frog lacks.
Recently male Pickerel Frogs have started calling to attract mates. Each species of frog, just like each species of bird, has its own distinctive call. Spring Peepers “peep, “ Wood Frogs “quack” and Pickerel Frogs “snore.” Their snore isn’t long – it only lasts a second or two — but it is unmistakable. Pickerel Frogs call from under water, as well as on top of mounds of vegetation, so if you hear one, and then search for it, you may not find it. To hear a Pickerel Frog, go to http://langelliott.com/mary-holland/pickerel_frog_VA.mp3. (Sound recording © Lang Elliott – langelliott.com & miracleofnature.org)
Starting with today’s post, my blog will occasionally be enhanced with the sound recordings of Lang Elliott. For those of you who may not be familiar with his work, Lang Elliott has made world-renowned recordings (that are commercially available) of the vocalizations of birds, mammals, insects, frogs and toads. If you’ve ever wondered what out-of-sight creature was singing, screaming, trilling or buzzing, his CDs and books will give you the answer. To learn more about the work of this author, speaker, cinematographer, sound recordist, and nature poet, visit http://www.langelliott.com.
Naturally Curious is supported by donations. If you choose to contribute, you may go to http://www.naturallycuriouswithmaryholland.wordpress.com and click on the yellow “donate” button.
Gray Treefrogs Calling
At this time of year, bird-like trills are often heard in wetlands, where male gray treefrogs (Hyla versicolor) are calling to potential mates. The chorus ramps up at night, but the songsters can be hard to find during the day, when they often hide in tree cavities or high up in the canopy. (Their large toe pads produce mucous which allows them to adhere to smooth bark.) The colors of a gray treefrog vary with the colors of its background and environmental factors such as season and humidity, but shades of gray are most common, with black blotches on the back. Variations of brown, green, and pearl-gray colors have been noted, with green being more prominent during the breeding season. Warm, humid weather seems to elicit calls from these well-camouflaged amphibians. To watch and hear a calling gray treefrog, go to http://www.youtube.com/watch?v=2kd5c4p8-0M. (Thanks to Rachael Cohen for photo op.)
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Wood Frogs Awakening and Thawing
The duck-like quacking of recently-emerged, courting wood frogs is slightly miraculous considering that only days ago these amphibians were frozen practically rock solid. At some point in late fall or winter, as temperatures drop, they flood their bodies with blood sugar that acts as antifreeze in their circulatory system. Activity in their brains stops, their heart stops, and 45 – 60% of their body can freeze. Yet within hours of being exposed to the spring’s warming temperatures, wood frogs thaw out and start moving towards a body of water to breed.
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Pickerel Frogs Calling
If you’ve spent time at a pond recently and heard what sounded like someone snoring, you weren’t hallucinating! Male pickerel frogs have started calling to attract mates, and each species of frog, just like birds, has its own distinctive call. Spring peepers peep, wood frogs clack and pickerel frogs snore. Their snore isn’t long – it only lasts a second or two — but it’s unmistakable. Pickerel frogs call from under water, as well as on top of mounds of vegetation, so if you hear one and then search for it, it’s very possible you may not find it. (My sincere apologies-computer failure prevented me from posting on the previous two days.)
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