Talks by Eric Angel Ramos
Bottlenose dolphins possess a wide repertoire of vocalizations and depend on sound for activities... more Bottlenose dolphins possess a wide repertoire of vocalizations and depend on sound for activities critical to their survival. The use of foraging-related calls has been reported but evidence for their use in most regions is absent. We observed the production of a distinct call that we termed “thrums” and conducted a study to investigate their acoustic characteristics and contextual use. During boat-based surveys from 2012-2013, we conducted surface and underwater behavioral observations and concurrently recorded acoustic signals during focal group follows. Thrums (n = 1381) were produced predominantly in the context of foraging behavior (96.7%) in 35.6 hrs of observations during 35 surveys. Thrums appeared harmonically structured with narrow-band energy concentrations in low-frequency bands (mean peak freq: 328 ± 185.9 Hz) and the majority (58.9%) possessed broadband frequency components in the ultrasonic range. Underwater observations revealed that dolphins produced thrums during bottom foraging in seagrass beds. The concentration of energy in the low-frequency range suggests thrums may function to manipulate prey behavior during a bottom foraging tactic in seagrass habitats.
Papers by Eric Angel Ramos
Frontiers in Marine Science, Oct 29, 2023
Signature whistle use and changes in whistle emission rate in a rehabilitated rough-toothed dolphin.
The Latin American Journal of Aquatic Mammals, Feb 29, 2024
Behaviour, 2024
In marine ecosystems, predators can affect community and ecosystem dynamics through a variety of ... more In marine ecosystems, predators can affect community and ecosystem dynamics through a variety of processes such as foraging facilitation. Here, we report evidence of foraging facilitation between common bottlenose dolphins (Tursiops truncatus) and double-crested cormorants (Nannopterum auritum) in the Caribbean seagrass-dominated atoll of Turneffe, Belize using aerial drone observations conducted in 2015-2017. While dolphins exhibited occasional aggressive behaviours toward the cormorants, the latter frequently followed dolphin movements, suggesting opportunistic pursuit of dolphins for prey access during dolphin bottom foraging activity. Our observations underscore the intricate ecological relationships among marine predators and highlight the need to quantify the mutual benefits and costs of such interactions as coastal ecosystems are rapidly changing.
PLOS One, 2024
To survive cold winters, Florida manatees (Trichechus manatus latirostris) depend on artificial (... more To survive cold winters, Florida manatees (Trichechus manatus latirostris) depend on artificial (i.e., power plants) and natural warm water sources such as springs and passive thermal basins. Passive thermal basins can provide critical habitat for manatees for short or extended periods of time. The Henry D. King Powerplant in Fort Pierce, Florida discharged warm water into Moore's Creek until it went offline in 1995. However, it is unknown to what degree manatees continue to occupy this area and how environmental factors influence their occurrence in the creek. To explore this, we examined the habitat use of Florida manatees in Moore's Creek after the shutdown from November 1997 to March 2020 from daily counts of manatees. In addition, we correlated local environmental data (ambient air, temperature, salinity) to assess if Moore's Creek had properties indicative of a passive thermal basin. Results indicated there was not an increase or decrease in habitat use over twenty years in the Creek. The consistent use of Moore's Creek over the study period suggests that this habitat possesses thermal and freshwater resources to support manatee occurrence long-term. These findings provide robust support for the importance of this habitat and passive thermal basins for Florida manatees.
Caribbean Journal of Science, 2024
Stranding events of marine mammals provide valuable opportunities to study their biology, health,... more Stranding events of marine mammals provide valuable opportunities to study their biology, health, and causes for mortality, such as interactions with predators. Here we document the stranding of a deceased adult spinner dolphin (Stenella longirostris) with a shark bite (possibly an injury) on Utila Island, Honduras. The findings may shed light on predator-prey dynamics and scavenging in the region.
Scientific Reports
Geographic variation in the vocal behavior of manatees has been reported but is largely unexplore... more Geographic variation in the vocal behavior of manatees has been reported but is largely unexplored. Vocalizations of wild West Indian manatees (Trichechus manatus) were recorded with hydrophones in Florida from Florida manatees (Trichechus manatus latirostris), and in Belize and Panama from Antillean manatees (Trichechus manatus manatus) to determine if calls varied between subspecies and geographic regions. Calls were visually classified into five categories: squeaks, high squeaks, squeals, squeak-squeals, and chirps. From these five categories, only three call types (squeaks, high squeaks and squeals) were observed in all three populations. Six parameters from the temporal and frequency domains were measured from the fundamental frequency of 2878 manatee vocalizations. A repeated measures PERMANOVA found significant differences for squeaks and high squeaks between each geographic location and for squeals between Belize and Florida. Almost all measured frequency and temporal parame...
ABSTRACTThis paper presents some unusual behaviors observed in one single specimen ofO. insularis... more ABSTRACTThis paper presents some unusual behaviors observed in one single specimen ofO. insularis. While nothing can be concluded rigorously from such data, we share the data and our analysis with the community, in the hope that others will be on the lookout for such rare events. Sleep is a fundamental biological function that is present in all tested vertebrates and most invertebrates.Cephalopods, such as octopuses, are cognitively complex animals that display active and inactive sleep states similar to those of vertebrates. In particular, octopuses have active sleep states during which they display sequences of camouflage patterns and modulation of basal rhythms, while remaining relatively unresponsive to outside stimuli. Some scientists have speculated that these states could be analogous to dreaming in mammals, involving episodic recall with a narrative structure. The convergent evolution of sleep in neurologically complex animals is a striking possibility, but its demonstration...
PLOS ONE, 2023
Many marine mammals exhibit diel trends in vocal production, which can provide information on hab... more 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.
Aquatic Mammals, Dec 1, 2016
Characterizing species occurrence, abundance, and distribution is critical to the management of n... more Characterizing species occurrence, abundance, and distribution is critical to the management of natural resources and the conservation of biodiversity. In the Western Caribbean, little information exists on the occurrence of aquatic mammals along the Mesoamerican Barrier Reef System and adjacent aquatic ecosystems. Herein, we present the first comprehensive review of aquatic mammals encountered in the marine and freshwater habitats of Belize. To determine which aquatic mammal species occur in Belizean waters, we conducted an extensive review of published and unpublished reports of aquatic mammals. We located 163 unique reports from museum and animal collections , journal articles, theses, news reports, conference proceedings, institutional reports, and verified accounts from personal observations. Our review confirms the presence of 17 aquatic mammal species in Belize: 15 cetaceans ((Trichechus manatus manatus), and one carnivore (Lontra longicaudis annectens). Our findings provide the most up-to-date list of aquatic mammal presence in Belize. Given the limited data points obtained for most identified species, we recommend that systematic studies be conducted to investigate the status of the variety of aquatic mammals in the region to effectively monitor populations and devise strategies to mitigate the negative impacts of anthropogenic activity and climate change-related ecosystem shifts.
Marine Mammal Science, Nov 26, 2022
Dorsal fins, one of the most notable dolphin's physical features, play important kinematic an... more Dorsal fins, one of the most notable dolphin's physical features, play important kinematic and hydrodynamic roles and are related to physiological and environmental adaptation processes. Differences in dorsal fin shape have been recently associated with geographic variation, habitat specialization between ecotypes, and ontogenetic factors. We studied dorsal fin variation across several common bottlenose dolphin populations in the Caribbean. A total of 252 dorsal fin photographs from eight coastal regions in the Caribbean were selected for analysis. Dolphin dorsal fin proportions were compared among regions and compared with data previously collected from Holbox, Mexico. Dorsal fin models were constructed for each region. We found that across the Caribbean, coastal bottlenose dolphins exhibit low variation in dorsal fin shape, with the most common dorsal fin pattern having low and triangular shapes, two traits that greatly contrast with the oceanic ecotype. Also, significant differences in overall dorsal fin proportions found among some adjacent groups support the hypothesis that subgroups could be present even within extremely short geographical distances ‐ as has been previously documented. The results of this study can be implemented in population monitoring efforts worldwide, as it uses free software and provides a step‐by‐step guideline to analyze the data.
Marine Mammal Science, Aug 2, 2021
Lay abstract: Bottlenose dolphins display diverse feeding behaviors. Here, we report mud ring fee... more Lay abstract: Bottlenose dolphins display diverse feeding behaviors. Here, we report mud ring feeding behaviors by bottlenose dolphins in an estuary shared between Belize and Mexico. We detected four mud ring feeding events in boat- and aerial-based observations. In visual searches of Very High Resolution (VHR) satellite imagery, we detected mud ring trails and mud ring feeding in Chetumal-Corozal Bay and confirmed their association with this tactic in Florida Bay. Feeding behaviors appeared similar in both regions and occurred in shallow nearshore habitats dominated by mud. Our results provide important insights into the development of foraging tactics in coastal dolphins.
Frontiers in Marine Science, Sep 12, 2018
Unmanned aerial systems (UASs) are powerful tools for research and monitoring of wildlife. Howeve... more Unmanned aerial systems (UASs) are powerful tools for research and monitoring of wildlife. However, the effects of these systems on most marine mammals are largely unknown, preventing the establishment of guidelines that will minimize animal disturbance. In this study, we evaluated the behavioral responses of coastal bottlenose dolphins (Tursiops truncatus) and Antillean manatees (Trichechus manatus manatus) to small multi-rotor UAS flight. From 2015 to 2017, we piloted 211 flights using DJI quadcopters (Phantom II Vision +, 3 Professional and 4) to approach and follow animals over shallow-water habitats in Belize. The quadcopters were equipped with high-resolution cameras to observe dolphins during 138 of these flights, and manatees during 73 flights. Aerial video observations of animal behavior were coded and paired with flight data to determine whether animal activity and/or the UAS's flight patterns caused behavioral changes in exposed animals. Dolphins responded to UAS flight at altitudes of 11-30 m and responded primarily when they were alone or in small groups. Single dolphins and one pair responded to the UAS by orienting upward and turning toward the aircraft to observe it, before quickly returning to their pre-response activity. A higher number of manatees responded to the UAS, exhibiting strong disturbance in response to the aircraft from 6 to 104 m. Manatees changed their behavior by fleeing the area and sometimes this elicited the same response in nearby animals. If pursued post-response, manatees repeatedly responded to overhead flight by evading the aircraft's path. These findings suggest that the invasiveness of UAS varies across individuals, species, and taxa. We conclude that careful exploratory research is needed to determine the impact of multi-rotor UAS flight on diverse species, and to develop best practices aimed at reducing the disturbance to wildlife that may result from their use.
Frontiers in Marine Science, Feb 12, 2019
Barragán-Barrera et al. Potential Distribution Stenella in Caribbean test values higher than 0.8,... more Barragán-Barrera et al. Potential Distribution Stenella in Caribbean test values higher than 0.8, indicating satisfactory model performance. The resulting potential distribution maps suggested that areas closest to continental shorelines of the Caribbean Basin and surrounding islands had the highest environmental suitability for all species (>70%). All models reported high environmental suitability for S. attenuata and S. longirostris in the SFBR, mainly in the southernmost part surrounding San Andrés and Providence Archipelago. Assessment of niche overlap from the predictions of species distributions using the similarity statistic and pairwise map overlap indicated that S. frontalis and S. longirostris had niches slightly more similar in comparison to S. attenuata. As this was a first effort to fill a gap in our understanding of the distribution of species in the genus Stenella in the Caribbean Basin, further studies are necessary using both niche modeling and biological/ecological approaches.
Ethology Ecology & Evolution, Sep 3, 2021
West Indian manatees (Trichechus manatus) are separated into two allopatric subspecies: the Flori... more West Indian manatees (Trichechus manatus) are separated into two allopatric subspecies: the Florida manatee (T. m. latirostris) and the Antillean manatee (T. m. manatus). In the winter of 2020-2021, an adult manatee was sighted off the coast of Cancun, Quintana Roo, Mexico, in areas where Antillean manatees are not typically seen. The individual had distinct watercraft scars on its body, which were matched using photo-identification to a known male Florida manatee (PE424) that had been repeatedly photographed in Florida since 1998. This is the first record of a Florida manatee visiting the Mexican Caribbean. Previous reports of individuals from this subspecies in Cuba, combined with genetic evidence, suggest some level of connectivity among geographically separated manatee populations.
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Talks by Eric Angel Ramos
Papers by Eric Angel Ramos