Amphibians
Hourglass Tree Frog
Dendropsophus ebraccatus · also called hourglass tree frog, hourglass treefrog
The hourglass tree frog is a small, pale, big-toed tree frog with a bold dark marking down its back — and an unusual habit for a frog: it does not commit to one way of laying eggs. Depending on the pond, it lays on a leaf above the water or straight onto the surface, weighing up drying out against being eaten.
Overview
Hourglass tree frogs live around ponds, ditches, and slow streams in lowland forest from southern Mexico to Ecuador. They are small, 2–3 cm, pale yellow to tan with a dark hourglass or bowtie mark down the back, and hunt small insects at night.
A frog that hedges its bets
Females can lay eggs on overhanging leaves or directly in the water, and which they choose tracks the local balance of risks: land eggs escape fish and aquatic predators but can dry out; water eggs stay moist but face fish and aquatic insects. Being able to switch lets the species breed successfully across a wider range of pond conditions than most frogs, which are locked into one strategy — making it a key study species for reproductive flexibility.
Status
The hourglass tree frog is Least Concern, common and widespread, breeding in everything from permanent ponds to small temporary puddles.
Hourglass Tree Frog: common questions
Why does the hourglass tree frog lay eggs both on land and in water?
Researchers studying this species found that the same population, and sometimes the same female across different clutches, will place eggs either on overhanging leaves above a pond or directly onto the water's surface, and which option is chosen tracks the risks present at a given pond. Eggs laid on land avoid the fish and aquatic invertebrates that eat eggs in the water, but they can dry out if rain is scarce and are exposed to different predators such as wasps and other insects. Eggs laid in the water are protected from drying but exposed to fish and aquatic predators. By being able to shift toward whichever option is safer at a particular site and season, the species can breed successfully across a wider range of pond conditions than a frog locked into a single strategy.
What does the hourglass marking look like, and does every frog have one?
Most individuals show a bold, dark brown or reddish marking down the centre of the back that narrows in the middle and flares at both ends, resembling an hourglass, a bowtie, or an hourglass-shaped shield, set against a pale yellow, tan, or greenish background, though the exact shape, colour intensity, and completeness of the marking varies quite a bit between individual frogs and even changes somewhat with the frog's activity and temperature, since like many tree frogs it can lighten or darken its base colour. The pattern likely helps break up the frog's outline against dappled leaves and bark.
How is this frog different from other small tropical tree frogs?
In basic appearance it resembles many small Dendropsophus and related tree frogs from Central and South America — pale, slender, with large toe pads for climbing, and a nocturnal, insect-eating lifestyle. What sets it apart scientifically is less its looks and more its behaviour, since the flexible, condition-dependent choice between terrestrial and aquatic egg-laying documented in this species is unusually well studied compared with most tropical frogs, making it a frequently cited example in research on how animals adjust reproductive decisions to immediate environmental cues rather than following one fixed inherited pattern.
Is the hourglass tree frog threatened?
No, it is listed as Least Concern. It has a fairly wide range across lowland Central America and the northern edge of South America, it breeds in a broad range of pond types from permanent ponds to small temporary puddles thanks to its flexible reproduction, and it remains common in much of that range, including in some disturbed and secondary habitats near forest. Like most tropical amphibians it could be affected by wetland drainage, pollution, and the spread of chytrid fungus, but it is not currently considered to be declining significantly or to need special conservation attention.