Which of the following can be classified as environmental stressors for animals?

Environmental stressors are factors in an animal's surroundings that can cause stress and affect their wellbeing. Humidity, noise, and odor are classic examples of environmental stressors because they pertain to the animal’s external environment rather than internal conditions. These elements can create discomfort or anxiety, leading to stress responses in animals.

Humidity can affect an animal’s ability to regulate its body temperature and can lead to heat stress. Excessive noise can frighten animals, triggering aversive reactions and impacting their willingness to engage with their environment or caregivers. Unpleasant odors can also create discomfort or anxiety; for example, a strong chemical smell can cause worry or distress in animals that are sensitive to scent.

While the other options present valid sources of stress, they are not classified as environmental stressors in the same context. Physical pain from injuries pertains to an animal’s internal state, and lack of food and water represents deprivation rather than environmental conditioning. Invasive medical procedures are about the interactions with caregivers and procedures rather than aspects of the immediate environment or surroundings. Understanding these distinctions is crucial for veterinary professionals aiming to create a less stressful experience for animals in their care.