Shenade Annie Kerketta, Amity University Kolkata
With the ever so growing human population, many animal species have been endangered and compromised. This article talks about Salt marsh harvest mouse, found in salt marshes of the San Francisco Bay Area in California. They are endangered species restricted to San Francisco Bay. The salt marsh harvest mouse has two subspecies northern subspecies (R.r.halicoetes) and southern subspecies( R.r.raviventris).
The southern subspecies are at a higher risk of being wiped out, so the study concentrated on these particular subspecies. The salt marsh harvest mouse (SMHM) is always mistaken for the Western harvest mouse (WHM) species. The western species is not endangered. They are similar in appearance to the salt marsh species, making it difficult to identify and save the salt mice. The study carried out educates us on the new accurate method devised to identify southern subspecies of salt marsh harvest mice.
The recent 2021 STUDY:
For the study, 204 harvest mice were trapped, from fourteen locations covering the bay area (northern and southern). Genetic information (hair) was extracted from each, along with the following parameters:
• Tail length
• Body length
• Total length
• Tail to body length ratio
• Tail diameter
• Mass
• Mass without pregnant mice
• Tail tip shape (blunt, intermediate, pointed)
• Ventral tail hair color (white, intermediate, tan)
• Tail pattern (bicolored, intermediate,unicolored)
• Ventral coloration(grey,intermediate,orange)
• Sex
This study included only adult mice. At the cytochrome b gene region, SMHM and WHM form reciprocally monophyletic clades. Sequence divergence greater than 10% was used to differentiate between SMHM and WHM.
This method of differentiation provided certainty. A multiple variable analysis was also, carried out to learn the importance of each morphological order. It also helped in discriminating the two species.
Different tests used to analyze data:
• t-tests were used to compare means for each morphological character.
• χ 2 tests of independence were used to analyze categorical characters ( ventral coloration, ventral tail hair color).
• R v.3.6 was used for statistical analysis and graphing.
• Random forest (Breiman 2001) was used for the multiple variable analysis.
The decision tree is a tree-like design of decisions and their possible results. It is a way to showcase an algorithm. It helps in evaluating all the possible options. The decision tree was used in this experiment to select characteristics that accurately identified a Salt marsh harvest mouse. Random forest test produces these decision trees through a machine learning approach.
Results and Discussion:
After carrying out all the necessary tests, the results turned out to be simple but very accurate. The characteristics which can accurately determine an SMHM are Ventral coloration (orange) and Ventral tail hair color (tan). This is why an SMHM is also known as ” red-bellied.” These factors can accurately differentiate between southern SMHM and WHM. The researchers also trapped mice in the northern bay area but, only WHM was identified. It means that there were very few SMHM in the Northern bay area. This test, therefore, studied only the southern SMHM accurately. Since the Northern SMHM is closely related to the Southern, the method will also work for the Northern population. Mice away from the test area were also collected to test the accuracy of their devised method. The experiment from the test area produced 97.8% accuracy and 97.3% accuracy with rats excluded from the test area.
Conclusion:
This study was to determine factors that could accurately differentiate an SMHM from a WHM. It turns out being “red” benefited the salt marsh harvest mice. This study produced excellent results, which can now efficiently help in the rescuing process of SMHM. They are an endangered species and, this experiment brought us one step closer to saving nature. Initiatives like this in this era are needed where we are desperately trying to save planet EARTH.
Also read: Romanesco cauliflower & its spiraling fractal shape
References:
- Statham, M. J., Barthman-Thompson, L., Fresquez, S., & Sacks, B. N. (2021). Development of a morphological key for the southern salt marsh harvest mouse using genetically verified individuals. California Fish and Wildlife Journal, CESA Special Issue, 367–381. https://doi.org/10.51492/cfwj.cesasi.22
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