Tag Archives: habitat restoration

De-Extinction: Horse Revival


A little baby horse named Kurt is a symbol of renewed hope for the survival of his kind. Born on 6 August 2020, he is the world’s first ever successfully cloned Przewalski’s horse, an endangered wild horse native to the steppes of central Asia. What makes Kurt even more exciting is that he was cloned from genetic material cryopreserved 40 years ago – reviving genetic diversity thought to have been lost decades ago…

Przewalski’s horses roaming the steppes declined dramatically after World War II, due to a combination of factors such as hunting, competition with livestock as humans moved into their territory, and severe winters. The last confirmed sighting of a Przewalski’s horse in the wild was in 1969. Luckily, some of the horses still remained in zoos. But not many. A total of 12 horses made up the ancestors of a captive breeding program – 11 Przewalski’s horses wild-caught between 1899 and 1902, and another caught in 1947. Thanks to this breeding program, there are around 2,000 individuals today. That’s incredibly impressive, but the growing population isn’t without problems.

Those 12 ancestor individuals represent what is known as a population bottleneck – when a species undergoes a severe reduction in numbers. From that point, a population can recover, but it can also be the beginning of the end. One of the reasons for that is lower genetic diversity. With less variation, a population is less able to adapt to potential stressors or changes to their environment…

Enter a Przewalski’s horse named Kuporovic, who lived from 1975 to 1998. An analysis of the captive breeding pedigree revealed that Kuporovic’s genome had unique ancestry from two wild founders. This meant he offered significantly more genetic variation than any of his living relatives, so in 1980, scientists took a sample and preserved it in San Diego Zoo’s Frozen Zoo.  San Diego Zoo partnered with wildlife conservation group Revive & Restore and pet cloning company ViaGen Equine to create an embryo using Kuporovic’s genetic material. This embryo was implanted in a domestic horse (Equus ferus caballus) surrogate, and was born healthy after a normal pregnancy.

Excerpt from Scientists Clone an Endangered Przewalski’s Horse For The First Time, Science Alert, Sept 7, 2020

When Restoration Is Eradication: Palmyra Atoll

On the Palmyra Atoll in the central Pacific Ocean, conservation biologists are in the midst of a massive, unprecedented experiment. They are trying to rid this remote island of all but a few coconut palms. The gangly tree is an icon of idyllic tropical islands, but also an aggressive invasive species that crowds out native plants and animals. By removing 99% of Palmyra’s millions of palms, biologists hope to create more room on the atoll’s three dozen islets for indigenous forests and seabirds, including the world’s second largest colony of red-footed boobies…

Red footed booby

Ripping out the palms has long been on the list of restoration projects on Palmyra. First, however, managers decided to attack another invader, black rats, which likely arrived on ships during World War II. With no predators, rats multiplied into the tens of thousands. They ate the seeds and gnawed the saplings of native trees and attacked seabird colonies, including those of sooty terns, which nest on the ground. Rats are the key suspects behind the absence on Palmyra of eight other species of ground or burrow-nesting birds, including shearwaters and petrels, all found on central Pacific islands that have remained rat-free. The first attempt to eradicate the rats in 2002 failed, partly because Palmyra’s abundant land crabs out-competed the rodents for the poisonous bait. The crabs’ physiology allowed them to eat the poison—the anticoagulant brodifacoum—without ill effect.

The second effort was successful only after [researchers] radio-collared rats and discovered that the rodents liked to hang out in the crowns of coconut palms. The crowns became a convenient platform for stashing cotton gauze sacks of poison bait, delivered by workers firing slingshots or dangling from helicopters. Crabs do not reach the palm tops.

Once rats were exterminated in 2011, researchers watched with delight as native tree saplings began to spring from the forest floor. There were also happy surprises. Scientists discovered two additional species of land crabs that had likely gone undetected because voracious rats suppressed their numbers. And researchers realized they were no longer being bitten by Asian tiger mosquitoes, a pest that attacks during the day and can carry dengue and yellow fever. It appears the mosquitoes depended on rats rather than humans or birds for blood meals…

Excerpts from Ridding Paradise of Palms, Science, Aug. 28, 2020, at 1047