Sam Carsdy of Oamaru asks :-

My daughter in Wellington recently discovered tiny tree frogs in baskets hanging about the eaves of her house. How do they get there?

Phil Bishop, a zoologist at Otago University, responded.

The frogs would be whistling tree frogs (Litoria ewingii) and were originally introduced from Australia more than 100 years ago.

Throughout the year, on cool wet nights, male whistling tree frogs will call close to small ponds to attract females to breed.

The females will lay hundreds of eggs which may take over a year for the tadpoles to develop into tiny frogs. They are very vulnerable at the water's edge when they do, so they try to get away from potential predators.

A nice place to shelter is in regularly watered hanging baskets.

There are several possible scenarios as to how the frogs got there.

It is most likely that the frogs were sheltering in the bases of the plants, in the soil or in the pot itself before they were transformed into hanging baskets.

Perhaps some of the material had come from a nursery, which is usually a good breeding site for frogs when large groups emerge from the water "en masse" to find shelter together.

If the hanging baskets were well established without new material being added in recent weeks, the frogs may have climbed up the walls (or wooden beams) and fallen into the baskets. With suckers on all their toes tree frogs can climb vertical window panes.

A third possibility is if the baskets were taken down for watering or pruning. Frogs recently leaving a nearby pond "en masse" might have colonised the "shelters" before they were re-hung.