Final answer:
Necropsies are performed more frequently on larger animals because they accumulate substances such as mercury from their prey, require specialized anatomical knowledge for post-mortem examination, and have different health challenges associated with their size and metabolic rate.
Step-by-step explanation:
The question of why necropsies are performed more often on large animals than small animals can be addressed by considering a few biological principles. Large animals, often being higher in the food chain, accumulate substances from the organisms they consume, which can lead to certain health issues. In addition, veterinarians require a deep understanding of different anatomies for various species, which influences the frequency and necessity of necropsies.
One consideration is the accumulation of various substances in the bodies of larger animals. For instance, larger animals may accumulate mercury (b) from consuming many small organisms that have, in turn, absorbed mercury from the environment. Over time, this can impact their health and necessitate the need for a necropsy to understand the extent of such accumulations and their effects on the animal's body. This issue is less prevalent in smaller animals and microorganisms (decomposers) that often have different dietary habits and lifecycles. Another aspect is the complexity and specialization of vertebrate species' anatomies. Veterinarians must understand these specialized structures and their functions to perform surgeries and necropsies effectively. For example, cattle have a unique four-compartment stomach, which requires specific knowledge to examine post-mortem, versus smaller animals that may have less complex anatomies. Furthermore, large mammals are of significant interest for conservation and public support, strengthening the case for performing necropsies to investigate the causes of death and promote species' wellbeing. Finally, the concept of metabolic rate is inversely related to body mass. Therefore, small animals like mice, with higher metabolic rates due to greater surface area-to-volume ratios, may have different health challenges compared to large animals like elephants. As a result, necropsies may be conducted with different frequencies and emphases based on these metabolic differences.