If a pika and a kangaroo rat switched environments, they might not survive for long due to their unique adaptations to their particular environments.
A pika's adaptation to its habitat includes growing thick fur in winter to conserve heat. In contrast, the desert environment where the kangaroo rat lives is very hot and dry; therefore, its oily fur helps to conserve moisture rather than heat. The pika's thick fur would make it too hot in the desert environment, whereas the kangaroo rat's oily fur would not be sufficient to conserve moisture in the colder environment.
Additionally, pikas get their water from consuming snow whereas kangaroo rats get water from seeds. In a colder environment, snow is readily available, but in the desert, there is no snow. The kangaroo rats might not be able to survive in colder environments if they do not have access to water, and the pika might not be able to survive in the desert without access to snow.
Therefore, it is likely that the adaptations that allowed the pika and the kangaroo rat to survive in their respective environments would make it difficult for them to survive if they were to switch habitats.