Many of them don't. However, in short-lived flash floods, echidnas can dive beneath the surface of the water, and retain enough oxygen to survive for a short while. Although they can swim, they are not built for endurance swimming, so cannot survive an extended flood.
Echidnas are not going extinct, so this is not an issue. They are highly adaptable to a variety of habitats, and as long as there is a ready food source of termites and ants, echidnas can survive in almost any climate found in Australia.
Given that echidnas have a conservation status of "least concern" throughout Australia, there are very likely to be as many echidnas in 5 years as there are now. It is unknown how many echidnas there are, but being a very adaptable animal that can survive wherever there are ants, it is expected the echidna has a very secure future.
Echidnas do not hibernate.
The biggest threat to echidnas occurs when they are young. Snakes will sometimes enter their burrow and eat the baby echidna. Other animals do not usually attempt to eat this spiky creature, but some echidna predators include very brave foxes and goannas. Echidnas are highly adaptable and less threatened by habitat loss than other native animals. Basically, echidnas can survive wherever there are ants.
Echidnas are one of Australia's native animals which have been least affected by human habitation. As echidnas feed on termites and ants, there is always a ready supply of these insects. However, this does not mean there is no effect on the echidna's habitat. Anywhere there is urban development is a threat to echidnas, whether this impact is by cars hitting the animals; echidnas being killed by domestic dogs; or building development such as bulldozers and other digging equipment. One of the major effects on echidnas is caused by flooding, often a result of humans changing natural watercourses by their activities. Echidnas can swim, but they cannot survive floodwaters.
No. Echidnas do not hop. They walk.
There are no echidnas in Bali. Echidnas are found only in Australia and on the island of New Guinea.
No. All echidnas are mammals, and all mammals are vertebrates. Echidnas are different from "echinoderms".
No. Echidnas eat termites.
Yes. Echidnas are solitary animals.
It is unknown how many echidnas there are in Australia. The echidna is common throughout Australia because it is very adaptable and can be found in all habitats, from sub-alpine regions to hot, semi-arid and arid desert regions. All it needs to survive is a ready supply of ants and termites to eat.
There's no collective term for a group of echidnas.