#zoobiquityproject

[alexasark]

Galapagos: Endemicity and Extinction

In almost every biology class, you learn about the Galapagos. Here Darwin studied a set of finches that spurred his theory of Natural Selection. Ironically, Darwin did not come to the Galapagos as a biologist per se. He was actually shipped off by his family with the hope that when he returned he might have discovered a greater sense of responsibility. I cannot attest much to his sense of personal responsibility, though we can all recognize that Darwin forever changed our perception of evolution.

The Galapagos served as a perfect location for understanding evolution. Between isolated islands, species (e.g. Darwin’s finches) differentiated to specialize in particular ecological niches. Darwin noted that there were similar but slightly different species on almost all islands. From here he reasoned they likely all had the same ancestor, but differentiated from them when they migrated to other islands, creating bottleneck effects and then selecting for mutations that were evolutionarily advantageous on that island.

Furthermore, animals that otherwise would not have survived in the presence of mainland predators, such as Boobies (which lay their egg on the ground), were able to thrive. Tortoises, without the presence of a larger herbivore, were able to grow to be much larger, thus evolving into Giant Tortoises, sexually selecting for height. 

With all these effects in mind, the Galapagos developed an extremely high rate of endemicity (estimated to be 40%, compared to an average of 5%). This makes the Galapagos Islands particularly susceptible to extinction because without other populations from around the world, once a species becomes extinct on one island, it is possible that it will never return.

While Darwin was in the Galapagos, he not only witnessed signs of adaptive radiation and natural selection (though these were not yet named phenomenons) but also current human-caused extinction. The Galapagos Islands served as a major stopping site for ships needing to refuel on fresh foods. Tortoises can live for up to a year without food and water. This made them the ideal shipping meat. They were carried on board (often by at least four men because they could weigh as much as 700 lbs) and then used throughout the trip as a source of food. While Darwin did not explicitly write about this human caused extinction, it is something he might have been aware of.

The tortoises dropped to dangerously low levels before they were protected. One subspecies, the Pinta Island Tortoise, died out completely a few years ago with its last known individual, Lonely George. Because the Pinta Island Tortoise is genetically only considered a subspecies, biologists are hoping to recreate or reintroduce the species on Pinta Island through DNA extraction of the most genetically similar tortoises from neighboring islands. 

The Galapagos Fur Sea Lions also came dangerously close to extinction. However with protection, the populations were able to recuperate (see video to come).

While visiting the Galapagos, I found myself reflecting on the present and the past. Three and a half million years ago, the islands were formed via a hot spot, and continuous west to east movement given the shifting ocean tectonic plate. Since then, life colonized, becoming more and more complex with each immigrant species and subsequent mutations. This gives rise to a set of islands that we use as the quintessential biological example of evolution. However, in a period with unparalleled extinction rates, how much longer will the Galapagos be able to exist as is? Given introduced species, marine ecosystem biomass decline with the crashing of fisheries, raising temperatures and sea levels, the Galapagos will likely become an example of the fragility of endemic existence. It may serve as only a history lesson unless dramatic changes are made.

This may sound like a doomsday forecast, but unfortunately, this is our reality. Many scientists have come to accept that we are living within the sixth mass extinction. If you want to read more, check out Elizabeth Kolbert’s The Sixth Extinction. It is a beatiful, information-filled book on past and current extinctions.

If you are more of a movie person, checkout Racing Extinction, which will be coming out in the fall. It is produced by the creators of The Cove, and is sure to be a very exciting and provocative depiction of our current environmental state of affairs.

If you are interested in what we can do to remmedy this, then please continue reading! Through veterinary wildlife medicine and compassionate conservation, I hope to expose and tackle many wildlife welfare issues that are resulting in species decline and eventual extinction! 

[alexasark]

If you are interested in more wildlife rehabilitation, here is a video of the release of successfully rehabilitated Red Shouldered and Red Tailed Hawks in Northern California. Watch carefully! Red Shouldered Hawks have an incredible ability to accelerate, as seen in this one’s release.

Notice the difference in setting. With the first release of the Red Shouldered Hawk, we chose a wooded area near a creek with plenty of shade. Red Shouldered Hawks thrive in these areas with smaller prey and not a lot of flying space, because they have the ability to accelerate so quickly. We released the Red Tailed Hawk in a much less wooded area, with more grasslands in the surrounding area. The Red Tailed Hawk will hunt slightly larger prey, like rabbits and gophers, and flies high above in the sky, watching the landscape from above, view unabated by foliage.

Red Tailed Hawks are much larger and do not have the same capacity for acceleration. Furthermore, as their name would suggest, Red Tailed Hawks have a redder tail when they are adults, while Red Shouldered Hawks have redder breasts and backs.

In a rehabilitation setting, hawks are one of my favorite species. Once you learn how to properly handle them (wearing very heavy and thick leather gloves), covering their head to reduce stress, you can really appreciate their physique. They have massive talons that are incredibly strong. Even through thick gloves, their strength is obvious. Their beaks are also incredible. Sharp and made for tearing, hawk’s beaks are distinctly curved compared to many other birds.

As patients, hawks can be challenging because they often do not eat well when they are stressed. We meticulously log how much of their food they eat, and force feed them if it comes to that. As always, we try to minimize handling and only intervene when absolutely necessary to limit their furthered exposure to humans.