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Trip Report for February 11th - 18th, 2012
Posted:Apr 29 2012 (All day)
Posted By:Eric Ramos
Greetings from the Oceanic Society Belize Field Station!
One of Blackbird Caye's residents, a brown vine snake (Oxybelis aeneus), made an appearance as we wandered across the field station on our way to the boat one morning. Grasping some long grasses on the right side of the path, this species can be found from the southern United States to South America. Alton picked up the slender reptile and after quickly coiling itself around his arm, it began to furiously protest its predicament and gave some benign bites to the hand. He released the snake in the bush where it slithered towards the tree-line.
Along the same trail a Spiny-tailed iguana (Ctenosaura similis) popped its head out of its comfortable abode atop a dead coconut palm. A hole bore out by Golden-fronted woodpeckers (Melanerpes aurifrons) suited the iguana well as it inspected the surrounding terrain, hastily retreating within the rotting trunk at the signs of dogs prowling the grounds.
Like clockwork the beginning of our third research trip of the year was met with some challenging weather. Windy though it may have been, mangrove cayes sheltered us much of the time as we traversed the shallow waters of the lagoon in search of bottlenose dolphins. Ginger and Elizabeth volunteered on our dolphin trip this week and a big group of snorkelers and volunteers for our Coral Reef Monitoring project kept the atmosphere at the station lively all week. Below are some highlights from this week early season trip.
Alton handling wild animals is a common sight on Blackbird Caye
February 14th - Valentine's day dolphins
A calm valentine’s day morning we set off from the station heading southwest of Harry Jones Cut into Long Bogue for our first trip of the week. Cruising at three to four knots, a light breeze blew as we glided over sand and seagrass. We attentively scanned the water's surface for some sign of cetaceans. Coming around a bend Alton suddenly slowed the boat; a good sign that dolphins may have been sighted. Standing alert we soon caught sight of an active group of dolphins near the edge of a mangrove caye. Splashes and fast darting suggested that part of the group was actively socializing.
Eight dolphins were in this group, a large group for this region. As often occurs, four individuals seemed much more preoccupied with each other than us or anything else in their environment. First positioning ourselves parallel to the group we got our photo ID shots, essential for identification of each dolphin. Alton steadied the boat in the shallows as Ginger and I observed and recorded their behaviors, many of whom were adults with a couple of juveniles and a mother/calf pair remaining ahead of the rambunctious crowd. Heads lolled at the surface, a mouth agape gave insight into the origin of much of dolphin scarring.
Flukes splashed at the surface and bodies rolled over at the top. Several males in the encounter gave us easy gender ID as they layed with their ventral surfaces facing up at the surface with clear view of their bright red genitalia. The image below captured a moment of sociosexual interaction between several males.
Some time into the encounter the contexts of these interactions began to emerge. Several individuals, with at least two males, were vigorously pursuing a smaller individual. Ton (TA169), a heavily scarred male, and Blotch (TA172), a male with a prominent dark spot along the trailing edge of his dorsal fin, attempted to mount the smaller dolphin, at times flanking the smaller dolphin on each side as it seemed to attempt to evade its suitors. Male bottlenose dolphins are known for their competition for reproductive access to females, forming alliances with one another to potentially improve chances for access to reproductively ready females. In some populations pairs of males have even been known to "herd" females by preventing her escape for up to several weeks. Gender ID of the third individual at some point in the future will be needed to confirm whether this may have been a sexual encounter for reproduction or the sociosexual kind.
Within an hour the vigorous socializing had ceased and five of the dolphins had departed leaving only Ton, Blotch, and another individual milling along the caye. A rare occurrence, assessing that there were no calves or intense activity in the water, Ginger and I were able to slip into the water with the dolphins. Once the data has been collected and condtiions are optimal it is sometimes possible to attempt to acquire gender ID of an animal by observing it's genital slit underwater. After kicking furiously to catch up to them we were able to get a glimpse of the group as they swam towards us, briefly inspecting before changing direction and slowly swimming forward.
We remained a comfortable distance from them, highly aware that this was not our world we were in; it was an aquatic world who's denizens should be afforded respect. Though we were not able to identify the sex of the third member of the group, we were grateful to have a chance to see the dolphins in their habitat first-hand. Several minutes into our swim they vanished into the shallows and we returned to the boat. Returning to the station, the trio were left quietly swimming into Fishing Bogue in waters three feet deep.
February 17th - A mangrove snorkel and dolphin run-in
Ginger and I inched along at our snorkel site along the eastern entrance of Fishing Bogue (image to your left). Turbid waters encircling the mangroves become crystal clear walls when you come face-to-face with the edges of the cayes. Here we find veritable displays of the biodiversity of life embedded in the labyrinth of the mangrove's roots. We entertained ourselves with the sights of bright orange sponges mushrooming from branching mangrove roots. Sea anemones and brittle seastars occupied the innards of the sponges with small fish and crabs craftily sliping away into the caye at our passing shadows. A long-snout seahorse (Hippocampus reidi) in bright yellow with brown bands along its back fastened to a root with with tail wrapped tightly. This tiny creature is often cleverly camouflaged amidst the mangroves where it feeds on the zooplankton and small crustaceans abundant in this ecosystem, but at the time it seemed a rather vibrant and conspicuous sight in the murky water.
After a time snorkeling along the edge of the mangrove habitat we turned towards the boat to Alton’s calls that a dolphin was here. Swimming hurriedly back and boarding Miss Callie, we set off behind a lone individual as it swam into Harry Jones Cut.
Luckily the dolphin was surfacing and making slow and prolonged exposures of his dorsal fin and flukes while making deep dives. With some fortunate surfacings we were able to identify the animal as Propeller; a resident male dolphin who is one of the few dolphins I find roaming the atoll alone. Only with us for a couple of minutes, his movements prevented a good of what he may have been doing but from the underwater footage we were able to see him swim directed towards the boat, turning abruptly, and rubbing himself against the bottom before swimming off.
Often when foraging and socializing the dolphins can be seen with parts of their body against the substrate, stirring up mud plumes where they make contact. With touch playing such a major role in dolphin sensory worlds, Propeller may have been simply engaging in a pleasureful activity, rubbing his sensitive skin against the silty substrate before continuing on his way east into Harry Jones Cut.
Big thanks to Ginger and Liz for joining our trip and supporting the research. Thanks to all of our guests for the week for coming down and supporting the station! Our volunteers make the on-going research possible.
More entries to come from this busy field season!
Eric Angel Ramos
Field Station Marine Mammal Biologist
Oceanic Society Belize Field Station
Blackbird Caye, Turneffe Atoll, Belize
Dr. Diana Reiss's Animal Behavior, Cognition, and Communication Lab
Department of Psychology
CUNY Hunter College
New York, New York
Visit our Belize Bottlenose Dolphin Project page to learn more about how you can support Oceanic Society and our scientific research by volunteering on our research trips to study bottlenose dolphins in Belize.