Predators wrongly blamed for losses, ancient Amami rabbits make a comeback
AMAMI, Amami-Oshima, Japan––The Easter 2019 bunny story of the year, and island ecology story, too, with even an angle involving egg hunts by ornithologists, is underway on Amami-Oshima and Tokunoshima islands, between Japan and Okinawa. Much to the evident embarrassment of the Japanese Environment Ministry, though, the bunny story is not following the script.
For starters, the officially endangered Amami rabbits are making an explosive comeback. But the free-roaming dogs, cats, and goats who were allegedly major threats to the rabbits’ existence are all still there in abundance.
Mongooses, the species most blamed for loss of rabbits, may still be there. The chief threat to the Amami rabbits at this point may come from disease, as the rabbit population is now possibly so dense that an outbreak of anything deadly to rabbits might rapidly spread.
An accidental introduction of rabbit hemorrhagic disease or myxomatosis, both repeatedly deployed in Australia and New Zealand by would-be island purifiers, could prove to be the biggest threat ever to Amami rabbits. Both rabbit hemorrhagic disease or myxomatosis have often been accidentally transmitted over long distances.
Though predators such as dogs, cats, and mongooses eat prolific herbivores such as Amami rabbits, the absence of predators can cause the prey species to decline much farther and faster. Sick animals in absence of predators to pick off the weak can easily infect the healthy––especially when expanding populations of prolific species are able to mix and mingle.
Dogs, cats, & goats
If the Amami mongooses are truly extirpated, dogs and cats may become the salvation of Amami rabbits when next disease strikes––and perhaps already have been, many times.
Dogs and cats appear to have been on Amami-Oshima and Tokunoshima islands for as long as humans have had a continuous presence, 1,500 years or more, meaning that dogs, cats, and Amami rabbits have had much time in which to behaviorally co-evolve.
The goats’ ancestors, however, were only released in 1966 to build herds for hunting and eating, then 78-year-old former community association chief Mitsushi Ikeshima recalled to the Yomiuri Shimbun newspaper in April 2006. The goats are believed to have directly impacted the Amami rabbits’ habitat.
Indian mongooses brought to protect goats
Amami rabbits are believed to prefer new forest growth areas for feeding, but old growth areas for nesting. Therefore Amami rabbits are most abundant in edge habitat where they can run back and forth from one type of forest to the other.
Though blamed for allegedly destroying edge habitat, by eating it, goats might in reality create more edge habitat, much like deer, by stripping bark from mature trees.
Be that as it may, the goats on Amami-Oshima and Tokunoshima islands proved vulnerable to four species of habu venomous snake. This led to the 1979 introduction of Indian mongooses, brought to the islands to control the snakes.
The habu snakes were and are believed to be the Amami rabbits’ chief natural enemies. The mama rabbits’ behavior of sealing their babies into underground burrows between nursings––and returning to unearth the babies and feed them only every two or three days––is believed to have developed to protect the young rabbits from habu.
Mongooses v. rabbits
Though the arrival of mongooses was expected to help the Amami rabbits, the mongooses apparently preferred eating rabbits to eating snakes.
Exterminating the mongooses, attempted since 2004, has coincided with the rabbits’ rebound. Yet the cause-and-effect of the situation may not be so simple. While introduced mongooses are widely blamed for depleting rare birds on various islands, especially parts of Hawaii and in the Caribbean, the real culprit afflicting rabbits on Amami-Oshima and Tokunoshima islands may have been development for tourism, especially building golf courses, that destroyed rabbit habitat.
Mongooses did consume habu to some extent, even though mongooses also ate rabbits.
And if any mongooses at all are left on Amami-Oshima and Tokunoshima islands, as seems likely, given the size of the islands, density of the forest remaining, and ruggedness of the terrain, the recent rabbit comeback could stimulate a mongoose comeback, and perhaps a habu comeback as well.
Amami-Oshima and Tokunoshima islands, part of Kagoshima Prefecture, are the only known habitat of the Amami rabbit, a relict species which appears to have split away from other Asian lagomorphs (the order including rabbits and pikas) about 20 million years ago.
Noted for smaller ears and shorter feet and hind legs than most rabbits, a bulkier body, and long curved claws used for digging and sometimes climbing, the Amami rabbit somehow survived and thrived on Amami-Oshima and Tokunoshima islands, even as all closely related rabbit species died out on the Asian mainland.
Both Amami-Oshima and Tokunoshima islands are of volcanic origin, hot, humid, almost entirely forested, frequently hit by typhoons, surrounded by coral reef, and sporadically inhabited by humans since Neolithic times. Records of continuous habitation begin in Japanese literature circa 600-700 CE.
Whale, bird, & frog-watching
Amami-Oshima and Tokunoshima islands together include barely 600 square miles of surface area. Amami-Oshima, the larger island, now has about 73,000 human residents. Tokunoshima, the smaller island, has about 27,000.
Their combined population density of 166 people per square mile is distinctly rural, but the city of Amami and seven other communities on the two islands are together attracting increasing tourism, especially to watch humpback and other whale species from cruise ships and to visit Amami Guntō Quasi-National Park, designated in 1974, occupying much of Amami-Oshima island.
Amami Guntō Quasi-National Park is home to Lidth’s jay, named from dead specimens by Dutch zoologist Theodoor Gerard van Lidth de Jeude (1744-1830), nearly annihilated by feather hunters and ostensibly still rare due to mongoose predation. Other rare species attracting visitors include the nocturnal Amami woodcock, the Ryukyu Scops owl, and a variety of unique indigenous frogs.
Mongooses have at times been blamed for suppressing the recovery of Lidith’s jay. Neither the jay, the woodcock, nor the owl, however, are known to be among cat or dog prey.
Rabbits protected since 1921––sort of
Concern for conserving the Amami rabbit emerged more than 40 years before Amami island had either feral goats or mongooses. Amami rabbits were initially depleted by hunting and trapping, as the human population of Amami-Oshima and Tokunoshima islands grew.
The Japanese government responded by declaring the Amami rabbit to be a “natural monument” in 1921. This stopped rabbit hunting, but not trapping, the greater threat to the seldom-seen rabbit, until a 1963 amendment to make the Amami rabbit a “special natural monument” ended legal trapping as well.
The Lagomorph Specialist Group of the International Union for the Conservation of Nature and Natural Resources in 1990 recommended various measures to rebuild the Amami rabbit population, but little was done until the Amami Wildlife Conservation Center, established in 1999 by the Japanese Ministry of the Environment, confirmed that Amami rabbits were still rare.
From scat counts to cloning
A photo collection extensively depicting the seldom seen rabbits, produced by photographer/conservationist Futoshi Hamada in 2000, brought public support for rabbit restoration efforts.
As of 2003, fecal pellet counts and surveys of sighting indicated, perhaps 2,000 to 4,800 Amami rabbits remained on Amami-Oshima island, and as few as 120 to 300 on Tokunoshima island. Amami rabbits were named to the Japanese endangered species list in 2004. The attempted mongoose purge began a year later.
Discovering rabbit bones in cat and dog feces, however, was not enough to put cats and dogs on the government hit list until a camera trap in July 2008 produced an image of a cat carrying the remains of a rabbit.
An attempt to clone Amami rabbits, publicized in November 2008, apparently failed.
“Kill the cats!”
A decade later, estimating the feral cat population of Amami-Oshima and Tokunoshima islands to be from 600 to 1,200––which could have extinguished the Amami rabbit population within a week, had it really been as low as was officially believed––the Japanese Ministry of the Environment decided to kill cats as well as mongooses.
The plan was to kill the cats at the rate of about 300 per year for 10 years, a pace which would actually not have reduced the cat population at all.
A nonprofit organization called Doubutukikin responded in August 2018 by initiating a neuter/return program.
That inspired Asahi Shimbun staff writer Masahiko Ohta to use the Japanese freedom of information act to obtain the official Environment Ministry survey data on the Amami rabbit numbers.
Rabbit count up fivefold to tenfold
Ohta published his findings on April 10, 2019.
The Amami-Oshima island rabbit population turned out to have been surveyed only once since 2003, in 2015, when the use of camera traps was added to the former method of counting scat and sightings.
As of 2015, Ohta wrote, “the rabbit population on Amami-Oshima was estimated at 15,221 to 19,202. Based on the [camera trap] method, the rabbit number is now estimated at between 16,580 and 39,780.
“Some experts say the ministry may have overestimated the rabbit population, given the wide range in the estimates,” Ohta added. “But Yuki Iwasa, head of the wild animal section of the ministry’s Naha Nature Conservation Office, said both estimates were conducted properly.”
Said Iwasa, “The number of Amami rabbits is no doubt on the rise,” Iwasa said. “Both approaches show there are at least 10,000 to 20,000 rabbits, and the estimates are consistent with observations by local staff.”
The increased Amami rabbit population may be downlisted from endangered to threatened status by 2023, Ohta suggested.
Cats are already vanishingly few
Eradicating cats from Amami-Oshima, according to the official plan, is expected to cost 500 million yen over a 9-year period, or about $4.5 million in U.S. dollars.
Responding, Doubutukikin and a variety of academic and nonprofit allies have petitioned the Japanese ministries of the environment and finance, the governor of Kagoshima Prefecture, and five mayors of Amami-Oshima island communities, requesting “immediate and total reconsideration of the ‘management plan on feral cats in Amami-Oshima island for ecosystem conservation (2018-2027)’ and suspension of killing the cats.”
Based on the 2003 data, the management plan “turned out to be lacking validity in light of current scientific study,” Doubutukikin charged, especially since, “During the 12 years from 2003 to 2015, the ministry only caught seven feral cats in 2012, and six in 2013. These facts clearly prove that cats were never a threat to Amami rabbits.”