The effects of dune plant roots on loggerhead turtle (Caretta caretta) nest success.

Sand dunes are supported by the extensive root systems of dune plants that anchor the dune and protect it from erosion. While all plants that grow on the dunes support their structure, invasive plants can outcompete the native and non-native dune plants for resources such as nutrients, sunlight, and space to grow. During the summer, sea turtles lay nests on beaches and near dunes; however, their eggs and hatchlings are at risk of destruction and entrapment by dune plant root penetration. Dune plant roots can penetrate sea turtle nest cavities, thus decreasing hatch success of the eggs and emergence success of the hatchlings. We aimed to determine how plant roots impact threatened loggerhead sea turtle (Caretta caretta) nests on Casey Key, Sarasota County, Florida, USA and to assess the factors affecting plant root invasion. Specifically, we determined the effect of plant roots on loggerhead sea turtle nest success, the extent of the impact of invasive plants over non-invasive plants on nests, and if the distance from the dune (barrier) affects whether roots will penetrate the nest. From July to August 2022, we excavated 93 nests to determine the extent of root penetration and identify associated plant species. This field campaign was supported by a long-term dataset (1987-2022) on loggerhead sea turtle nesting across the region. We found that root presence decreased hatch success by 21% and emergence success by 18%, compared to nests that lacked roots within the nest chamber. Nests closer to the dune were more likely to have a higher proportion of root damage and lower hatch and emergence success. This study helps advance understanding of how native and non-native plants affect sea turtle reproductive success and helps inform coastal management aimed at conserving threatened loggerhead populations.

Manatees display diel trends in acoustic activity at two microhabitats in Belize.

Many marine mammals exhibit diel trends in vocal production, which can provide information on habitat use and behavioral activity. In Belize, Antillean manatees (Trichechus manatus manatus) commonly inhabit small depressions in the substrate or deep-water coves known as "resting holes". Determining if manatees exhibit diel temporal trends in their call production rate and call types between microhabitats can provide insights into their diurnal and nocturnal activity patterns. Here, we investigate the diel vocalization patterns of wild Antillean manatees in two adjacent resting holes off of St. George's Caye, Belize. Recordings of manatees were made using a bottom-mounted hydrophone located near a reef barrier reef for nine days in July of 2017 and ten days in January of 2018. To explore if and how manatee acoustic activity differs between sites, we compared the number of calls per hour, the number of manatee positive hours, the number of tonal and atonal sounds, and the number of boats detected across sites. A total of 370 hours of acoustic recordings were analyzed resulting in the detection of 3,262 calls. There were no significant differences in the number of manatee calls produced per hour between sites. The average number of calls produced by manatees decreased over the course of several days. The proportion of tonal calls decreased with hours after sunset and increased in boat presence. These results suggest manatees in this region may exhibit different diel activity patterns which appear to be influenced by the characteristics of the environment. These findings can support ongoing conservation and management efforts to safeguard species in Belize.

Antillean manatee calves in captive rehabilitation change vocal behavior in anticipation of feeding.

Captive animals typically develop anticipatory behaviors, actions of increased frequency done in anticipation of an event such as feeding. Anticipatory behaviors can be an indicator of an animal's welfare. However, for rehabilitating animals that are expected to be reintroduced into the wild, these behaviors need to be extinguished to ensure successful release. Scheduled activities such as feeding occur daily and vocalizations could potentially be used to identify anticipatory behavior. Here, we tested the hypothesis that manatee calves modify their vocal production rate as a form of anticipatory behavior. Vocalizations of two Antillean manatee (Trichechus manatus manatus) calves were recorded for 10 min before, during, and after feeding sessions at Wildtracks, a manatee rehabilitation center in Belize. The number of calls were counted across recording sessions and three acoustic parameters were measured from calls including duration, frequency modulation, and center frequency. A repeated measures ANOVA comparing the number of calls across sessions indicated manatees produced significantly more calls before feeding sessions than during and after sessions. In addition, manatees increased the duration and lowered the frequency of calls before feeding sessions. This information can give further insight on ways to improve rehabilitation protocols and manage human interactions to increase the overall survival rate of rehabilitated manatees when released back into the wild.