Each year, millions of animals enter animal shelters across the United States and are met with a variety of potential stressors that can negatively impact their experience, including noise, confinement, and social isolation. Foster care, a unique form of human-animal interaction, is increasingly understood to be an effective tool for improving welfare by allowing animals to escape the stressors of the shelter, providing an environment that allows for greater social interaction, and offering opportunities for improved health and behavior. This review includes 42 published articles, reports, master's theses, and doctoral dissertations that have previously evaluated companion animal foster care programs. While scientific literature in this area has increased over the last decade, no review of the research exploring companion animal fostering has been published. Here, we examine foster care programs and their effects on human and animal welfare, evaluate the successes and challenges of supporting shelter foster care programs, recommend best practices for programmatic success, illuminate discrepancies in equity and diversity of caregiver engagement, and offer directions for future research in animal foster caregiving. The examinations in this review conclude that fostering provides both proximate (i.e., physiological and behavioral) and distal (i.e., length of stay and adoption outcomes) welfare benefits for shelter animals as well as their caregivers. Companion animal foster care programs may be further improved by providing greater caregiver support and increasing the diversity and extent of community engagement. Meanwhile, scientific investigations should explore lesser-researched components of foster care programs that are not yet well understood.
