In 1870, 12 rusa deer arrived from Java, and legend says the governor of Java sent them as a diplomatic gift. According to a 2024 study in the European Journal of Wildlife Research by Alain Frantz and colleagues, the entire island population descends from those 12 founders. The team cites an estimate of between 250,000 and 370,000 deer, a figure from 2011.
Invasive species often sneak in by accident. In New Caledonia, a French island territory in the South Pacific, the story was quite different.
The new home of the deer was very different from their home in Java. The herd then grew rapidly. In savannas and dry forests, they reach particularly high numbers. The team sees the animals as a major threat to the environment. Browsing by deer, the study shows, can stop natural regeneration of dry forest, and the animals also lead to soil erosion by overgrazing and bark stripping from trees. So what then do the deer eat? The review’s authors, Michel de Garine-Wichatitsky and colleagues, pulled together reports, expert answers, and early field surveys. But the thorns and spines did not keep the deer away. The review adds that more research was needed to confirm these results. Their results suggest that deer form one genetic population on Grande Terre. males were found wandering While females remained close to their homes. The landscape hardly affected their movements. In other words, there was little on the island that prevented deer from moving around freely. This is important when it comes to management. In practice, the authors warn, removing deer from a specific priority area can be undone by deer migrating in from surrounding areas, and reducing their numbers may be impossible without substantial funding.
Native plants in New Caledonia evolved without the presence of grazing animals, including deer, according to a 2003 review in Pacific Conservation Biology . Frantz’s team calls it a dramatic expansion, putting the population at over 200,000 by 1940, a figure they credit to that review. New Caledonia is a biodiversity hotspot, with more than 3,400 species of vascular plants recorded, the researchers note. Some 74% are found only on these islands. The menu included many types of plants: 25 grasses, 15 forbs, 26 trees and shrubs, and 12 vines and ferns. Nearly half (49%) of the principal and preferred food plants were alien species, while 56% of the plants the deer avoided were native.
Today, the deer inhabit nearly every land habitat on the main island, Grande Terre.
