For which species is an adjunctive method of euthanasia recommended due to difficulty in detecting heartbeat?

The recommendation for an adjunctive method of euthanasia for small rodents arises from their size and physiological characteristics that make it difficult to reliably detect a heartbeat. Small rodents have high metabolic rates and a rapid heartbeat, which can complicate the assessment of cardiac activity, particularly in a laboratory or research environment where immediate confirmation of death is critical.

In scenarios involving small rodents, it is essential to ensure that euthanasia methods are effective and humane. Since heartbeats in these animals can be challenging to monitor accurately, complementary methods—such as confirming cessation of respiratory or brain activity—are often advised to guarantee the animal's death has been achieved. This approach aligns with ethical standards and regulations governing animal welfare, ensuring that researchers are providing appropriate care and humane treatment.

In contrast, fish and amphibians present their own unique challenges, but the context of this question specifically points to small rodents' difficulty in heartbeat detection as the need for adjunctive euthanasia methods. Nonhuman primates, due to their larger size and physiological characteristics, generally have clearer indicators for assessing vital signs than small rodents.