The Bawean hog deer is the rarest deer in the world. It's only found on the small Indonesian island of Bawean and is considered 'critically endangered' — with an estimated population of less than 300 individuals.

Bawean hog deer are nocturnal and known to walk along well-trodden paths through thick foliage — moving in a crouch with a hog-like gait (hence the name). They often return to the same bed of vegetation for several days in a row. Both sexes bark, and their vocalisations can be heard up to 100 metres away through the dense forest. When separated, a mother calls to her fawn with a cry, and the fawn responds with a high-pitched squeak that only carries over short distances. Hunting this deer has been illegal since 1977 — it is one of 25 priority species legally protected by the Indonesian government — but the species is still threatened by dogs. Observations over a two-year period found that feral dogs were responsible for 9 out of 11 Bawean hog deer deaths, making them the leading cause of mortality. Of the 55 deer species, only two are critically endangered: the [giant muntjac](https://www.inaturalist.org/taxa/74660-Muntiacus-vuquangensis) of the [Annamite Mountains](https://www.worldwildlife.org/magazine/issues/summer-2024/articles/wildlife-of-the-central-annamites) and the Bawean hog deer. As of its [last evaluation](https://www.iucnredlist.org/species/2447/73071875) in 2014, the Bawean deer population is considered stable. **You can learn more about this rarest of deer from** [**my website here!**](https://www.curiousspecies.com/my-species/bawean-hog-deer)

Japanese dwarf flying squirrels glide using special skin flaps called patagia—they can soar from tree to tree like tiny forest gliders!

The bald parrot is a species that lacks any head feathers — apart from some sparse bristles. Endemic to the east-central Amazon, its baldness might be an adaptation for eating fruit without getting its feathers sticky.

From early sightings, the bald parrot was thought to be the juvenile stage of another species — perhaps a young [vulturine parrot](https://www.inaturalist.org/taxa/73326-Pyrilia-vulturina) (a slightly-less-bald parrot).  In 1999, some "immature" parrots were caught and examined, and were found to have fully developed skulls and gonads; meaning they weren't immature at all, but an entirely separate species. Some young birds go bald during an awkward feather moult, some go bald from disease or mites or stress-induced feather pulling. The bald parrot is just bald, perpetually.  Why? Why of all the \~400 parrot species are the bald and vulturine parrots the only ones with naturally featherless heads? One hypothesis posits that it's so they can eat fruit without getting sticky pulp stuck in their head feathers. Or maybe the bare skin helps them cool down in their balmy rainforest homes. It could also be the result of sexual selection. Perhaps it's the sum of all three.  **You can learn more about this parrot, and other bald birds, on** [**my website here!**](https://www.curiousspecies.com/my-species/bald-parrot) *\**[*Pesquet's parrot*](https://ebird.org/species/pespar1)*, also known as the vulturine or Dracula parrot, does show some facial skin, but it isn't bald.*

The speckled eggs in this nest are from the Brown-headed Cowbird, North America's most common "brood parasite".

The Chacoan peccary was initially described as an extinct species from fossils discovered in 1930. In the early 1970s, a living population was found in an isolated area of Paraguay — in a region known as the Gran Chaco. This species is the largest and rarest of the three living peccaries.

This peccary was assumed dead upon discovery — the species was described from fossils found in northern Argentina in 1930, fossils dating to the Pleistocene epoch (2.6 million to 11,700 years ago). For over a century, science recognized two living species of peccaries: the [collared peccary](https://www.inaturalist.org/taxa/42113-Pecari-tajacu) and the [white-lipped peccary](https://www.inaturalist.org/taxa/42115-Tayassu-pecari). Then, in the early 1970s, a "fossil" peccary was seen roaming an isolated area of Paraguay, in a region known as the Gran Chaco. The Chacoan peccary is the largest of the living peccaries, standing up to 69 centimetres (2.2 ft) at the shoulder and weighing as much as 40 kilograms (90 lb). It lives in the Dry Chaco and has well-developed sinuses for breathing the dusty air of its arid home, along with tiny hooves that allow it to tiptoe through thorny shrubs. Much of the Chacoan peccary's diet is made up of succulents. It plucks their spiny morsels, rolling them around with its snout to remove their prickly parts or pulling the spines out with its teeth before munching on the juicy, green flesh. It digests its meal in a two-chambered stomach, while its specialised kidneys break down the excess acids. Afterwards it treks to a salt lick — a mineral-rich rock formed from a leaf-cutter ant mound. Chacoan peccaries live in families of up to ten individuals, who travel, take midday naps, and dust-bathe together. They also face danger together; forming a living wall, raising their spiny fur, grunting and chattering their teeth when confronted with a threat. This species, returned to us from the Pleistocene, is now threatened with habitat destruction, as natural forests are cleared for pasture and soy plantations (much of that soy going to feed livestock in Europe). There are currently estimated to be 3,000 Chacoan peccaries left in the wild, and the species is considered '[endangered](https://www.iucnredlist.org/species/4015/72587993)'. **You can learn more about this prehistoric not-pig\*, and what’s being done to protect it, on** [my website here!](https://www.curiousspecies.com/my-species/chacoan-peccary) \**Peccaries, also known as javelinas, are a related but separate family to the suids — the pigs.*