If Only Squirrels Could Talk...

Wednesday 19 December 2012

13:03 - No comments

St.Kitts Rodent Recovery Day 93

With the difference between the two populations determined, I have completed my job for the Department of Nature and Island Resources of the West Indies. I have been contacted by my employers and my report has been accepted. 

I uncovered that there are two species of squirrel, the Sciurus kittus and the Sciurus nevisus due to specific prezygotic reproductive isolation barriers - those being behavioral isolation and habitat isolation. I also determined that a possible reason for the split between these similar species is allopatric speciation, with the earthquake that split the two islands apart hundreds of thousands of years ago that caused a separation of the original species.

Additionally, a possible reason as to why such a decrease in Sciurus kittus population may have to do with the numbers of cashew nut trees still remaining on the island. These squirrels are most commonly found on wild cashew trees and due to their removal for new development space, as well as the interference of hungry humans, the squirrels are forced to search for new suitable homes. In that period, many may have died and will continue to die.

In order to save these rodents, the Department of Nature and Island Resources of the West Indies is encouraged to immediately start a captive breeding program to save the population on the island of St. Kitts. Once the population has grown, they can be re-released into the wild and live once again. The environment of the island must be preserved and less upset by development and tourism in order for this decrease to not occur again.

12:49 - No comments

St.Kitts Rodent Recovery Day 80

Now that I have ascertained that the Sciurus kittus and the Sciurus nevisus are two different species, I decided to dig deeper into their history, and see what caused the speciation of these rodents. After looking at geologic records, I learned that St. Kitts and Nevis Island were once a combined land form many, many years ago. 

Numerous earthquakes had split the island by a result of the moving of tectonic plates, which was a long, slow geological process. Nevertheless, over this time, Allopatric speciation occurred, which divided the one species into two. The original homogenous population became separated due to the splitting of the land and both groups slowly diverged from each other because of their own evolutionary course, the accumulation of gene mutations, as well as natural selection. 

And so, after several hundreds of years, these animals evolved and changed so significantly that they could no longer mate between each other.

12:45 - No comments

St.Kitts Rodent Recovery Day 68

There has been a new discovery regarding the speciation of the Sciurus kittus and the Sciurus nevisus. After further exploring the habitats of each species, it has another form of prezygotic isolation was revealed – habitat isolation. Though both species live on trees, I have discovered that Sciurus kittus prefer to live on cashew nut trees (Anacardium excelsum) that are often located close to the ground whereas the Sciurus nevisus are found on taller more dense trees such as star apple trees (Chrysophyllum cainito).

Cashew Tree

Star Apple Tree

Though the reason behind this has yet to the explored, the two species preferences for different habitats help maintain their isolation. 

It is hypothesized that, besides the taste preferences, since St. Kitts rodents are able to reach a higher top speed than the Nevis Island rodents, they have higher chances of escaping ground predators so they don’t require as much protection from the trees.

12:27 - No comments

St.Kitts Rodent Recovery Day 58

With these new findings, I have decided to assign names to each species of rodent. Since the rodents from each island are common bushy-tailed tree squirrels, they belong to the genus Sciurus. Named after their island habitats, the St. Kitts Rodent is now called Sciurus kittus, while the Nevis Rodent species is called Sciurus nevisus. Creative, isn’t it?

12:16 - No comments

St.Kitts Rodent Recovery Day 56

Whew! It’s been a long time since the last update but gee, there have been some significant findings, that’s for sure. After trying 240 times to bring a Nevis Animal into the St. Kitts population, I have determined that it mating them is not possible, for there are several prezygotic reproductive barriers. 

Upon closely inspecting the courtship process of each animal, it is seen that there is an obvious behavioral isolation – the rodents of St. Kitts have an average courtship display that lasts approximately 12.6 seconds, whereas the Nevis rodents have a courtship display that lasts 21.3 seconds! Due to the difference in the length of each ritual, it seems that they are unable to attract each other.

Additionally, the average measurements of the St. Kitts rodent, and the Nevis rodent were obtained, and here are the results:

 

Though they have the same body patterns and shape, these rodents vary slightly in size and physical ability. Thus, due to these reasons, it appears to be that the St. Kitts Rodent and the Nevis Rodent are two different species.What a finding!