According to World Wildlife Fund, endangered tigers face unrelenting pressures from habitat loss, poaching and retaliatory killings. They are forced to compete for space with dense and often growing human populations. ©Surya Ramachandran
The Pyrenean ibex (Capra pyrenaica pyrenaica) officially became extinct in January 2000, when a falling tree landed on Celia, the world’s last wild Pyrenean ibex. Unfortunately, what led up to that unhappy incident was a sad history for this wild mountain goat.
Several species of ibex once lived across Africa, Asia and Europe. They coexisted with humans for a long time; painted ibexes have been found on the walls of caves in southern Europe that date back 30,000 years and at sites in Israel’s Negev Desert from at least 10,000 years ago. The subspecies known as the Pyrenean ibex moved into the mountains of northern Iberia and southern France around 18,000 years ago, near the end of the last Ice Age, along with a few other closely related subspecies.
Hunting, inbreeding and other factors ultimately caused the animal’s extinction. The case of the Pyrenean ibex is a powerful example of species loss due to causes related to human activity. But strangely enough, the melancholy story of these wild goats could mean a ray of hope for other endangered animals: it could help us save today’s wild tigers.
Pyrenean ibex were a subspecies of Iberian ibex—also known as the Iberian wild goat, Spanish ibex or Spanish wild goat—shown here, that today live on the Iberian Peninsula. There were four subspecies of Iberian ibex; two are now extinct: the Portuguese subspecies became extinct in 1892, and the Pyrenean subspecies became extinct in 2000.
Pyrenean ibex: genetically analyzing historical biological collections
While it’s likely that the tale of the Pyrenean ibex is the first extinction event of the 2000s in Europe, it can give us valuable information on what should be done (or avoided) to halt the extinction vortex we’re currently in.
The first official mention of a Pyrenean ibex, a subspecies of Iberian ibex, was in a written document from 1767. At that time, it already referred to the animal as extremely rare. Like many other mountain goats, the Pyrenean ibex was almost hunted to extinction before its killing became prohibited in 1913. But neither the institution of a national park in Spain (Ordesa y Monte Perdido) in 1918 nor a conservation project with the LIFE program (the European Union’s funding instrument for climate action and the environment) could stop the animal’s extinction, officially declared on January 6, 2000, when that tree fell on Celia.
Recently, a team of researchers from seven nations endeavored to find out more about the drivers of the Pyrenean ibex’s extinction. They built a database of all known museum specimens and reconstructed the demographic history of the Pyrenean ibex based on DNA evidence. Their research was published in the science journal Zoosystematics and Evolution on April 1, 2021.
Ordesa y Monte Perdido National Park is located along the border of France and Spain. The original park, created in 1918, only covered the Ordesa Valley with the intention of conserving Pyrenean ibex.
The scientists found that after a population expansion between 14,000 and 29,000 years ago (which is quite recent from a genetic point of view), Pyrenean ibex experienced a significant loss of range and genetic diversity, which started about 15,000 to 7,500 years ago. Eventually, the animal’s distribution was reduced to only one valley in the Spanish Pyrenees, which became the Ordesa y Monte Perdido National Park.
Written sources confirm that the Pyrenean ibex was hunted from as early as the 14th century; and during the 19th and 20th centuries, the ibex became a common target for trophy hunters. Undoubtedly, hunting played an important role in the animal’s demise, but researchers believe it is not possible—with the information currently available—to pinpoint it as the straw that broke the camel’s back. For example, infectious diseases that originate from livestock (such as those caused by the bluetongue virus or Sarcoptes scabiei, the itch mite) are capable of decimating other subspecies of Iberian ibex in extremely short periods of time.
While the relative contribution of various factors remains largely unknown, it seems that hunting and diseases transmitted from other animals have been effective in drastically reducing the number of Pyrenean ibex over the last two centuries because they were acting on an already genetically weakened population. Low genetic diversity, combined with inbreeding depression and reduced fertility, brought the population beyond the minimum viable size. From that point onward, extinction was inevitable.
Wild Bengal tigers live only in Bangladesh, Bhutan, India and Nepal. In a densely populated country such as India, human-wildlife conflict is a big problem. Although people are often willing to move away from tiger habitats to safer areas, moving large numbers of people is costly, difficult and time-consuming. ©Sai Adikarla, flickr
This recent Pyrenean ibex study demonstrates the importance of historical biological collections for genetic analyses of extinct species. Even private individuals may possess items of high value; a privately owned, 140-year-old specimen preserved in Pau, France, was genotyped as part of this research. As there is little knowledge of such resources, the study’s authors call for the creation of an online public database of private collections hosting biological material for the benefit of biodiversity studies.
I think such a move would keep the Pyrenean ibex from having died in vain.
Tigers: mating between subspecies for genetic rescue
So, although now gone, Pyrenean ibex might be able to help today’s tigers.
Despite being one of the world’s most charismatic species, tigers face an uncertain future, primarily due to habitat fragmentation, human-wildlife conflicts and poaching. And as global tiger populations decline, of course, so does their genetic diversity.
The majority of remaining wild tigers are isolated, unconnected to other populations and face escalating human encroachment into their territories. Tigers are also increasingly exposed to unfamiliar diseases through interactions with domestic or feral animals. ©Surya Ramachandran
To find out how the animals’ dwindling numbers are affecting them at the genetic level, researchers at the National Center for Biological Sciences in India, at Stanford University and at various zoological parks sequenced 65 genomes from four of the six surviving tiger subspecies (Amur—or Siberian—tiger, Bengal tiger, Indochinese tiger, Malayan tiger, South China tiger and Sumatran tiger). Their findings, detailed in a report published in the journal Molecular Biology and Evolution, confirmed that strong genetic differences exist between different tiger subspecies; but surprisingly, these differences emerged relatively recently, as Earth underwent a major climatic shift and our own species grew increasingly dominant.
According to the researchers, the world’s existing tiger subspecies began exhibiting signs of dramatic contractions starting around 20,000 years ago, a period that coincided with both the global transition out of the Pleistocene Ice Age and the rise of human dominance in Asia. Each subspecies of tiger that the team studied showed unique genomic signatures because of their increasing isolation from one another.
For example, local environmental genomic adaptation to cold temperatures was found in Amur tigers, the northernmost tigers that live in the Russian Far East. These adaptations were absent in the other tiger subpopulations studied. Meanwhile, tigers from Sumatra showed evidence of body size adjustments, which could help explain their overall smaller measurements. Despite these adaptations, tigers from these populations have low genetic diversity, suggesting that if they continue to decline, genetic rescue may need to be considered.
In the past 100 years, tigers have lost more than 93 percent of their historic ranges. Although still globally endangered, the International Union for Conservation of Nature states that there has been an average increase of the tiger population within protected sites by 40 percent between 2015 and 2021. ©Surya Ramachandran
One form that genetic rescue might take is through the mating of different tiger subspecies as a way of increasing their genetic diversity and protecting against the ill effects of inbreeding. Inbreeding occurs when populations are so small and isolated from other populations that related individuals breed with each other. Over time, this leads to lower genomic diversity and to the emergence of recessive diseases, fertility problems and physical deformities that often result in behavioral, health and population declines. Although increasing genetic diversity is one goal, another might be to select for inherited traits that confer higher survival in a changing world.
Even Bengal tigers from India, which comprise about 70 percent of the world’s wild tigers and exhibit relatively high genomic diversity compared to other subspecies, showed signs of inbreeding in some populations, conclude the study’s researchers. Some Bengal tiger populations are essentially small islands surrounded by an inhospitable sea of humanity. These tigers cannot disperse and so have only their close relatives to choose as mates.
Genomes: gleaning down to the subspecies level
Both the studies with the extinct Pyrenean ibex and with the tigers show that genomics is a valuable conservation aid. They also make clear that examining diversity within species is critical.
The Pyrenean ibex may be gone, but they left a legacy: they show us how genomics can help guide conservation efforts for endangered wild tigers and other species. ©Surya Ramachandran
Some populations within a species are well adapted to a future dominated by humans and our new climates and others are not, so any type of wildlife management should be informed by what we can glean from their genomes. The researchers say that the increasing dominance of humans across the world means that our understanding of which attributes of species and their various populations are best suited to the Anthropocene becomes ever more important.
I believe that when dealing with the sixth mass extinction, wild goats and untamed tigers show us that it’s not only the species as a whole that we need to consider, but their subspecies, as well. It could mean the difference between conservation failure and extinction, or success—and a little ray of sunshine.
Here’s to finding your true places and natural habitats,
Candy
