Owl Pellet Lab Analysis/Conclusion

In this lab, we were given an owl pellet which we dissected to find the remnants of the organism that the owl had consumed. We first took down the mass, length, and width of the pellet as 5.82 g, 3.7 cm, and 3.0 cm respectively. Then using forceps and a probe we separated the bones in the pellet from the fur, making one pile of each. Using the key on page 15 in our dissection lab handout and measurements of the bones we found, we were then tasked with deciding what animal it was. Unfortunately, we were unable to find enough bones to piece together the entire skeleton of our organism, but we found enough evidence to make a claim as to what it might be.

Claim: From the results of this lab, we concluded that the skeleton we found in our owl pellet most likely belonged to a mouse.

Evidence: The skull we found has teeth with a gap (diastema) between the incisor teeth and molar teeth. Because these teeth - when inspected under a dissecting microscope - had a rounded shape with no visible roots, we could narrow down that the skeleton belonged to either a rat or a mouse. Because the length of the skull was less than 25 mm (it was 15 mm) and the length of the lower jaw was between 9-16 mm (it was 11 mm), we concluded that the skeleton belonged to a mouse.  In addition, the hip bones we found were similar to images of mouse hip bones shown on page 16 of the lab handout.

Reasoning: Following the steps of the dichotomous key on Page 15 of the lab manual, we went from step 1 to step 2 to step 3 to step 4, ending at (b) of step 4. In this way, we were able to conclude that the skeleton we found belonged to a mouse. In addition, the bones we found in the owl pellet matched the images and scale of what mouse bones should look like, as shown on Page 16 of the lab handout. Both, the dichotomous key on Page 15 and the pictures of various rodent bones on Page 16 helped us reason out that the organism was most likely a mouse.

The skeleton of the shrew we found could be compared to that of a human.
Some similarities we noticed between the mouse and a human skeleton were:
(1) The mouse skull and human skull shared many structural similarities - the structure of the jaw/mandible was similar and the location of the eyes, mouth, and nose, were similar in both skulls.
(2) The mouse hip bones (tibia, fibia, and femur) which we pieced together very similarly matched the anatomy of the human hip bone.
(3) Both, the mouse skull and human skull have teeth with similar structures and the teeth are found in the same place in both the mouse and human skull.

Some differences we noticed between the mouse and a human skeleton were:
(1) The mouse skull has a gap (diastema) between the incisor and molar teeth, which the human skull does not have.
(2) The human skull is longer vertically, whereas the mouse skull is longer horizontally.
(3) The human eye socket is circular, whereas the mouse skull we found had more oval-shaped eye socket.