Peepers herald the beginning of a new season
Columnist Annamarie Hatcher tells us about the spring peepers.
The Mi’kmaw word for May is Squoljuiku’s which translates to ‘frog croaking time.’
The scientific name for the Jijawej (northern spring peeper) reflects its distinguishing feature. The species name ‘crucifer’ means crossbearer, because of the obvious X on their little backs. They are tiny frogs, weighing in at about 4 grams with a body length of about 30 mm, which is slightly larger than a twoonie. Although the spring peeper is often called a tree frog because of its toe pads for climbing, it is usually hidden in the dense vegetation and leaf litter around ponds and swamps at ground level.
In the Bras d’Or Lake Biosphere, the first calls of the northern spring peeper are anxiously awaited as they herald a much-anticipated change in the weather. Northern spring peepers can be found from southeastern Canada throughout the eastern United States as far south as northern Georgia. That allmale, love-sick chorus starts in March in the southern end of Nova Scotia but not until April and May in the Bras d’Or Lake Biosphere.
The Jijawej symphony that you hear near swamps and bogs is a chorus of the desperate cries of male peepers longing to attract a mate. After they awake from their winter’s sleep, males will call fairly consistently at temperatures ranging from 4 to 21o C. The females listen intently but do not call back. The louder cries come from the older, larger males who are anxious to pass their genes to the next generation before the end of their short life. Northern spring peepers begin breeding in the first year after they have hatched and can live an estimated three years in the wild.
That loud harmony near the pond represents a balance between singing a love song for a female and defending a singing spot from a male neighbour. The singing Romeo changes from a gentle chirping sound to a more threatening, rising trill when a male neighbour starts to invade its space. The sounds are made by inflating a vocal sac under the chin which expands and deflates like a balloon. Although it can be heard throughout the day in some places, the peeper chorus rises in intensity at dusk and dawn when amorous activities are most vigorous.
Why do the peepers raise their voices now and how can they muster up so much enthusiasm so early in the spring? Two of our frogs, (wood frogs (Mi’kmaw: Samqwani’j)) and spring peepers, are anxious and ready to go as soon as the weather warms. They overwinter in the Biosphere, surviving freezing temperatures (down to -8 C) that are fatal to most other frog species. Spring peepers hibernate during the winter in soft mud near ponds, under logs and in holes or loose bark. In the late fall, when temperatures near the freezing mark, they make their own
anti-freeze. They mobilize glucose from their livers which causes blood glucose levels to increase dramatically. The glucose acts as a natural anti-freeze for fluids around vital organs. Frozen fluids are confined to outer parts of the body. Final ice contents as high as 70 per cent of the total body water content can be tolerated by these freeze-tolerant frogs. Unique cell membranes allow efficient movement and compartmentalization of the glucose-rich fluids. Frogs that are not freeze-tolerant lack these adaptations. The heart of the frozen frog stops but is capable of starting up again with the gentle spring warming. At that time, the internal fluids re-distribute around the body and the little heart starts beating regularly after the body thaws. All body systems are then re-animated and the little male spring peepers start
their desperate cries for love.
The faster and louder the male spring peepers sing, the greater the chances of attracting a mate. Females lay anywhere from 750-1,200 eggs which are attached to submerged plants. Males are happy to fertilize the eggs as they are laid. Depending on the temperature, eggs can hatch within two days to two weeks. The tiny tadpoles have gills to breathe underwater and tails to help them swim. They will metamorphose into young frogs and emerge in August and September, joining their relatives hiding in the thick cover of plants circling the water. During the summer and autumn the adult peepers live relatively solitary lives, being mostly active at night and during moist, warm days. They don’t travel far, with home ranges that are from one to six metres in diameter.
So, what determines which ponds might make the best love-nests for these thawed peepers? In the Bras d’Or Lake Biosphere there are many suitable spring peeper habitats. The best ponds are ones that are mainly open with encircling grass and small shrubs. Nearby sugar maples produce a rich soup of water entering the pond which will fuel the aquatic food webs. Other trees such as oaks produce runoff that is not as attractive. A rich diversity of habitat provides a variety of perches for the male chorus and hiding places for the young tadpoles. Interconnecting ponds at the edge of a hardwood forest are ideal!
Amphibians are indicators of environmental change. Please help us keep an eye on the health of our Biosphere populations. Become a Frogwatch volunteer. Register at:
This diagram of the spring singers is by Annamarie Hatcher.
This photo shows a northern spring peeper and can be seen at http:// novascotia.ca/museum/amphibians/image.asp?id=75&spec=frogs.