Factors To Extinction


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If seeing the great animals of Africa is on your wish list, go as soon as you can! 

I recently led a Seminars in the Sun group to South Africa with wildlife expert Dr. Peter Brothers. His guidance and lectures gave us insight into the complexity and multilevel challenges that Africa faces to preserve its amazing biodiversity and heritage as the birthplace of man.

Malayan sun bears may become extinct sooner than expected, two ecologists say.

The most disturbing concept for me to absorb is the heartless process of extinction. It happened to the dinosaurs after a huge meteor hit the planet. It happens as life proceeds. It is happening now despite desperate conservation measures.

Many factors come into play, such as weather, habitat loss, environmental toxins, disease, shrinking population dynamics. These factors can be analyzed to predict extinction risks and rates for endangered species. But some species may become extinct much faster than predicted because scientists have not updated the standard extinction prediction model.

Alan Hastings at the University of California, Davis, and Brett Melbourne at the University of Colorado in Boulder are ecologists who believe that conservation organizations are using outdated extinction models for their predictions. They urgently recommended a re-evaluation of the risks to wildlife based upon the proportion of males compared with females in a dwindling population, and the differences in reproductive success between individuals and birth rates in the group.

When Hastings and Melbourne factored these additional aspects into risk assessments for particular species, they found that the danger of extinction substantially increased.

They demonstrated that missing factors such as the number of males to females and variations in the number of offspring are capable of causing unexpected large swings in the size of a population. At times, the swings may cause a population to grow, but they also may cause a population to contract. 

This deterministic viewpoint on extinction was detailed by Melbourne and Hastings in the July 3, 2008, issue of Nature. The ecologists contend that older extinction models could be erroneously underestimating the time to extinction. They predict that some species could go extinct 100 times sooner than expected.

The human-animal bond will not be able to hold these endangered species on the planet unless we intervene.

The new extinction models were tested in Melbourne’s laboratory by studying different types of randomness in dwindling populations of beetles. To format the new extinction model, the researchers mathematically combined the influence of weather and the random births and deaths of a reduced population.

For example, the environmental fluctuation of not having enough wind may speed the extinction of the salmon populations off the West Coast of America. The salmon numbers are down. This is because the usual wind-driven upwelling of nutrients and organisms from the depths to ultimately nourish the salmon did not occur. A few years with poor winds negatively affect the salmon population.


According to the IUCN’s 2007 report, more than 16,000 species are threatened with extinction.


After analyzing extinction risks that combined weather and randomness into the new model, Hastings and Melbourne found that some species may have only a few months instead of a few years left on the planet. This is because threatened animal populations will need a much higher number to be safe from the effects of these random processes.

The ecologists predicted that the Sumatran tiger and Malayan sun bear, the smallest of the bear family, may disappear much sooner than expected. They also found that other species not identified as under threat should be placed on the endangered list.

The International Union for Conservation of Nature (IUCN) uses older extinction models to create the annual “red list” of endangered species.

The Yangtze River dolphin was listed as critically endangered in 2007 but could be already extinct.

About 1.8 million described species are in the world but only 41,000 are being monitored. According to the IUCN’s 2007 report, more than 16,000 species are threatened with extinction.

This translates to one in four mammal species, one in eight bird species and one in three amphibian species. The IUCN also evaluated the world’s coral reefs based on surveys of more than 1,000 species and found many of them in dire distress.

During our journey to wildlife reserves, Dr. Brothers had us  participate in conservation work projects. Theriogenologist Dr. Hank Bertschinger allowed us to help immobilize wild dogs for examination, vaccines, blood draws and collar placement. The collars contained a pheromone that might reduce aggressiveness.

We participated in a conservation project with Dr. Heinz Kohrs and field researcher Heike Zitzer. They asked Dr. Brothers to deliver gonadotropin inhibitors via dart gun to calm the reproduction efforts of the largest bull elephant at the White Elephant Safari Reserve.  

Dr. Brothers spoke about African animals hunted for ivory and trophies to near extinction. Great herds of African animals were hunted and driven off their millions of acres of natural woods and pastureland as man encroached with farms and ranches to settle South Africa. We learned about the great conservation efforts and the work it took to reintroduce the elephant and the rhino back to South African game preserves.

The November 2009 issue of National Geographic mapped seven areas in the world that have endangered crocodilian species. It is expected that a few species will become extinct in the next 10 years or so.

Alice Villalobos, DVM, DPNAP, is a past president of the American Assn. of Human-Animal Bond Veterinarians and is president-elect of the Society for Veterinary Medical Ethics.

This article first appeared in the December 2009 issue of Veterinary Practice News

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