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TO: NMFS et al HERZING FROM: DR. DENISE LE: FEB 22 2009 DATE: Stenella frontalis at MMC Sunday, Feb 22 2009 10:00 I arrived at MMC at 10am. This dolphin was still in the small pool. After observing it for an hour both in and out of the pool I would conclude that it is a S. frontalis. Although this individual could still be a hybrid, it is a dilute one if that. ( I would still check for cross with T. truncatus and even S. attenuata). The physical features indicate pure S. frontalis to me. However, the size of this individual would indicate that it is well over a year old. If this were an individual S. frontalis from the community I study in the Bahamas I would estimate him at least 3-5 years of age. However, he has little to no spots which is very unusual unless he is a offshore/deep water ecotype. All his behavior says to me he is a coastal Atlantic spotted dolphin. It is possible that the community off Key West inhabits deeper water sometimes and individuals are slow to spot, as is the case in other parts of the world. I have seen the offshore ecotype in the Bahamas and they virtually have no spots, are group animals, and act more like spinner or pantropical spotteds than coastal Atlantic spotteds. The dolphin at MMC is calm, measured, and does not seem, behaviorally like an offshore variety. In our Bahamas community we do have a few individuals (very small percentage, maybe 3%) that have very few ventral spots for their age, so there is some natural variation. To me the size is more indicative than the spots for aging this dolphin because of the variation in the degree of spotting according to depth. And little is known about the populations off of Key West and the Gulf of Mexico except for occasional NMFS cruises. 1130 am. Dolphin moved to the lagoon. I entered the water shortly after to listen for any vocalizations. None were heard although physically he was moving his head, indicating scanning. Again, this is not unusual in murky water to have dolphins potentially “listen” vs. echolocate. (Or it is possible his echolocation is ultrasonic). We see spotteds in the Bahamas with bad visibility not echolocating and it appearsto indicate passive listening. He was calm and cautious at first, but after two hours was clearly exploring the edges of the lagoon and even trying to drag and play with some floating leaves. His breathing patterns were stable and normal. After observing him from a higher platform he seemed to be scanning the bottom and the edges of the lagoon. At one point he pointed vertically to the sand and some kicked up sand was observed, indicating that he might be exploring or digging under the sand. This is very typical for the coastal variety as many of their prey items are under the sand in shallow water (flounders, razorfish, conger eels, snakefish). He also took the prepared fish when thrown in front of him by the staff, so he appears to be eating solid food just fine. 1315. I listened to various acoustic recordings made during his 5 days in the pool. I plan to look at them more closely in the coming week, but from my first impression, this dolphin used his raspy “signature” whistles extensively during the initial period in the pool. He also produced echolocation click trains, with a clear terminal buzz, usually indicative of the last stages of prey capture. Young calves do produce these sounds in the exploration of prey, without ingestion, although the sound trains are not usually as consistent in a calf as they are in an older animal and as I heard on the recordings. It is also not unusual to see older dolphins mock-target certain fish, especially the species they do not eat. He made no sounds that I heard either in the pool or in his lagoon area. It will be important to see if he can still vocalize if given the chance to chase live prey. But it should not be surprising if he does not eat the fish as the prey may not be a normal menu item for him in the wild. 1400. I left the facility. I am interested to hear if he is still able to vocalize. It is possible that without any response to his “contact” calls or signature whistles he just gave up trying. Playback of his sounds, or other spotteds or random sounds, st in acoustic communication. might be worth trying to see if it reactivates his interest in accoustic communication.
1.He physically looks to be S. frontalis. My best guess is that this dolphin is a coastal Atlantic spotted dolphin, around 4-5 years of age, from a community that has a light degree of spotting, or alternatively he is one of the small percentage of this type that naturally has little to no spots onthe ventral side. I do not think he is a calf (birth to 3 years). His behavior is not atypical of a dolphin that is separated from its group. In my experience, even adult spotteds separated from the group can whistle despondently as this individual did in the early days in his pool. This coastal type of spotted is also very calm and slower in movements, and comfortable in shallow areas, like bottlenose dolphin (as opposed to deep water animals like pantropical spotteds or spinners). S. frontalis are a gregarious and curious species, searching out tactile behavior and other species when needed. Behaviorally, if he starts vocalizing and exploring the sandy bottom this would be a good sign. I would also expect him to use his echolocation for chasing live fish if provided. As far as reintegrating into a group of spotteds it is possible. However, I don’t know how likely it is to encounter a group near shore where he was found, nor do I think the genetics would indicate reintegrating him in a community of known spotteds in the Bahamas (not to mention the possible medical issues). We do have emigration and immigration in our resident community in the Bahamas. This occurs usually with juvenile males his age, however they are always is a small coalition of 2-3 individuals. And sometimes they are unlikely to integrate even in this scenario. Personally, I am not a big believer in releasing a lone dolphin, unless you could verify which group he came from around Key West. On Interspecific Interactions and Integration This individual was sighted with a small group of local apparently bottlenose dolphins at one point. In the Bahamas we have regular (15%) of the time interspecific interactions between spotted and bottlenose dolphin, and much of it is affiliative, not always aggressive. I am not aware of any baseline of the potential interspecific interactions off of south Florida, although Randy Wells and group have some occasional sightings of the two species together off of the Sarasota area. There are a few instances of long-term reintegration ie..of a young spinner with bottlenose in French Polynesia, so that is a possible scenario to consider. We have identified one hybrid in the Bahamas between Atlantic spotted and bottlenose (by morphological features) and Kim Parsons (geneticist) has preliminarily identified crosses between coastal and offshore bottlenose dolphins in the Bahamas. So hybridization is not impossible, and it is likely more prevalent that suspected. We also have other suspected hybrids in our Bahamas group that we are trying to verify genetically.
Species/Health Denise Herzing |