Bedding Type Modulates the Effects of Postpartum Resource Scarcity on Maternal Behavior in Rats

Resource scarcity paradigms are widely used to model environmentally induced disruptions in rodent maternal behavior. Yet, the critical methodological variable of bedding substrate type has received limited attention despite substantial variation in its use across laboratories. This study examined how two distinct bedding types (corncob, cellulose) interact with scarcity-adversity to influence maternal behavior in postpartum rats. We report that scarcity-adversity reliably increased insensitive pup-directed behaviors, elevated stress-related behaviors (tail biting/chasing), and impaired pup retrieval performance across both bedding types, confirming that resource scarcity disrupts maternal care regardless of substrate. However, the specific pattern of behavioral effects differed across bedding conditions. Increases in pup shoving were specific to scarcity-adversity dams in corncob bedding, whereas increases in anogenital licking of pups were specific to scarcity-adversity dams in cellulose bedding. Independent of adversity, cellulose dams displayed greater percentages of time spent grooming pups and nest building, while corncob dams displayed greater percentages of time spent nursing. In the pup retrieval test, cellulose dams exhibited longer latencies to retrieve 70% of pups than corncob dams. Together, these findings suggest that while core scarcity-adversity effects on insensitive pup-directed behaviors and pup retrieval generalize across these two substrates, bedding properties shape the specific expression of maternal behavioral disruption. Cellulose bedding may partially buffer certain aspects of intended adversity through compensatory caregiving, while corncob bedding may compound adversity through substrate discomfort. We recommend reporting bedding type in resource scarcity studies to facilitate cross-laboratory comparisons and ensure substrate characteristics align with experimental goals when modeling postpartum environmental adversity.