Welcoming a new vessel to the Sarasota Dolphin Research Program fleet: R/V Challenger

Bottlenose dolphin health assessments are a valuable tool to evaluate individual dolphin health and provide insight into stressors that are impacting the overall ecosystem.  Blood sampling for health evaluation began in 1987 to develop medical histories for the known resident dolphins and provide baseline data for comparison to other free-ranging and managed dolphin populations.

Over the past 26 years since these initial blood data were collected, SDRP researchers, in collaboration with a team of biologists and veterinarians, have developed protocols for clinical evaluation of individual dolphins that minimizes dolphin handling time, optimizes safety and sample collection, and provides a quantitative methodology for assessing the overall health of a dolphin population.  Many of the samples collected for this assessment require immediate processing in the field to ensure that subsequent laboratory analyses are not compromised.

To meet these needs, SDRP researchers began searching for a suitable platform that would serve as a “floating laboratory” to process samples efficiently in the field and provide the highest quality data for laboratory analyses.  The ideal vessel would have a large, stable working platform with good airflow to permit centrifuging of blood tubes, pipetting of serum and plasma, and fine-scale processing of samples while in the field.

After an intensive search, a vessel was located that fit this description, a 24 ft. Sun Tracker pontoon boat, built one year after the first blood samples were collected in Sarasota, in 1988.  The pontoon boat was extremely well cared for and had an open design, which allowed for ample table space to process samples.  A new 90 hp Yamaha 4-stroke was added to the pontoon boat to provide enough power to carry its sampling crew and gear as well as keep up with the rest of the health assessment fleet.

The pontoon boat was named the R/V Challenger in thanks to the Community Foundation of Sarasota County’s Giving Challenge, which raised a large portion of the funding needed to purchase and outfit the vessel, and as a salute to the HMS Challenger expedition of 1872-76 which was a global scientific research cruise that made some of the first discoveries in the field of oceanography.

This article was published on page 48 in the January 2014 Nicks n Notches.

Ultrasound evaluation for pregnancy determination and fetal evaluation in Sarasota Bay dolphins

Ultrasound is a rapid and noninvasive tool for examining the female reproductive tract in bottlenose dolphins.

Techniques have been established to evaluate the ovaries, uterine body, and uterine horns of the female dolphin with ultrasound.

In the case of pregnancy, a fetal assessment is also performed to determine the approximate gestational age and health of the dolphin fetus.  These techniques are extremely valuable and informative, as there is no other way to definitely diagnose a pregnancy and accurately assess the health of a developing fetus.

Ultrasound has been used for decades to evaluate the reproductive status of Sarasota Bay dolphins, and techniques continue to improve over time with increased sonographer experience and advances in ultrasound technology.  During the Sarasota Bay health evaluations, all female dolphins are quickly evaluated to determine if they have the potential to be reproductively mature.  This is generally based on total body length as a rough estimate of age.  If the dolphin is either suspect or confirmed to be old enough to be pregnant, an in-water reproductive ultrasound exam is performed.

Exams are typically performed with the ultrasound technician and ultrasound machine positioned on the stern gate of the research vessel, and the sonographer is partially submerged in the water to allow easy access to the animal.  The sonographer wears heads-up display video goggles, more commonly used by video game players, to view the ultrasound image in bright sunlight.  The research team gently restrains the dolphin while the sonographer quickly gathers sonographic data on the reproductive tract and status.

The ovaries are examined for the presence or absence of ovarian structures, specifically follicles and corpora lutea (CL).  Follicles are typically evidence of active cycling behavior; however large solitary follicles may be cystic.  CLs most commonly represent pregnancy, but can also be consistent with an active cycle in a non-pregnant female or a disease process.  If follicles and/or a CL are detected, images are captured and the structures are measured.

Any evidence of pregnancy, including a CL with or without uterine fluid, warrants close inspection of the uterine horns for an embryonic vesicle or fetus.  If a fetus is detected, the biparietal skull diameter is measured and the fetus staged according to skull size.  An estimated due date can be calculated based on the skull diameter.  The fetus is further evaluated for viability based on a heartbeat, fetal movement, and basic organ definition.  If time allows, motion (M) mode is utilized to measure fetal heart rate, which is another indicator of fetal health.  Color Doppler can also be used to interrogate the umbilical cord vessels, the fetal heart, and great vessels to document presence or absence of blood flow.

Upon return of the research team to land, all images captured during the in-water exam are then reviewed in a dark room to facilitate more thorough evaluation of the sonograms and measurement of significant structures when appropriate.  If needed, additional review is performed by the veterinary sonographer with a marine mammal veterinary radiologist.  During this review, final ultrasound interpretations are made and abnormalities are recorded.

During 2012-13, the SDRP was funded by NOAA’s Marine Mammal Health and Stranding Response Program to compile and examine Sarasota Bay dolphin data collected since 1989 from ultrasound exams for pregnancy determination.  The project involved identifying which cases were observed to result in calves that survived long enough to be observed during regular monthly photographic identification surveys, in order to provide an estimate of the proportion of observed fetuses reaching successful parturition.  Preliminary analyses indicate that about 85% of dolphins with diagnosed pregnancies were subsequently observed with calves.

Understanding female reproductive status, fetal health, and estimated due dates add great value to understanding dolphin population health and behavior.  These data also inform the way animals are handled during their health exam, tracked during the months to follow, and scored with regards to overall health.   We will continue to gather these critical data during future health evaluations, and Sarasota Bay health data will continue to be utilized as the baseline reference values for female reproductive health, pregnancy outcomes, and success in comparisons with other bottlenose dolphin populations, including those potentially impacted by oil spills and other pollutants.

 

This article was published on page 18 in the January 2014 Nicks n Notches.

Comparing dietary consumption of iron in wild dolphins vs. those in managed collections

Iron storage disease has been reported in a large variety of managed collections of mammal species.

Differences in the amount and bioavailability of iron between natural forages and provisioned diets are most often cited when discussing possible etiologies for iron storage disease among affected species.

Our research goals were to compare the iron levels in the blood of wild and managed dolphins and to analyze fish for iron content from their native and non-native diets. Using this information, our goal was to determine if there is a correlation between diet and iron levels in dolphins.

Dolphin blood values for total iron, AST, ALT, and GGT were compiled from wild and captive populations. The wild population consisted of 180 individuals (93 males, 87 females) ranging from 1 year to 50 years old, provided by the Sarasota Dolphin Research Program. The managed collection data were collected from 12 cooperating marine mammal facilities. The managed population consisted of 118 individuals (58 males, 60 females) with an age range of less than 1 year of age to 59 years old.

Seven species of native fish from Sarasota Bay were used in the study (ladyfish, mullet, pigfish, pinfish, seatrout, spot, and toadfish).  In total, 46 samples of native fish caught during 2009-2012 were analyzed for iron content.  Native fish were caught during fish monitoring surveys conducted by the Sarasota Dolphin Research Program. Six species of non-native fish were used in the study from the managed population diets (herring, capelin, smelt, sardines, mackerel, and saury).  In total, 109 samples of non-native fish from 2009-2012 were analyzed for iron content.

Wild dolphins’ iron levels decreased with age with a slight increase in advanced age. Managed dolphins’ iron levels increased with age. The native diet had an average iron consumption of 22.03 ppm per day and non-native (managed) diets ranged from 16.4 ppm – 17.5 ppm per day. It appeared that managed dolphins consumed less iron than wild dolphins. Wild and managed dolphins’ diet values were based on the average proportions of prey items consumed as reported. Further research is needed to determine the cause for iron overload observed in select dolphins that consume a non-native diet.  Funding for this research was provided by the 2012 International Marine Animal Trainer’s Association (IMATA) research grant.

This article was published on page 17 in the January 2014 Nicks n Notches.

Sarasota Bay dolphins provide clues to prevent insulin resistance in dolphins and humans

Dolphins can naturally switch diabetes-like states on and off.

In some cases, however, dolphins can develop diseases similar to people with insulin resistance.

In collaboration with the National Marine Mammal Foundation (NMMF) and the Sarasota Dolphin Research Program, a three-year study supported by the Office of Naval Research aims to identify dolphin groups that may be at higher and lower risk of insulin resistance. By doing so, the investigators hope to target new ways to prevent and treat insulin resistance in dolphins.

A new panel of tests was developed and used with Sarasota Bay dolphins to assess their metabolic health. Compared to other groups, Sarasota Bay dolphins had lower insulin, glucose, cholesterol, and triglycerides. These results support that Sarasota Bay dolphins may be better protected against developing insulin resistance compared to other dolphin groups managed under human care. The investigative team is currently exploring how Sarasota Bay dolphin diet, activity, genetics, and environment may prevent insulin resistance. These studies, led by Dr. Stephanie Venn-Watson at the NMMF and SDRP’s Dr. Randall Wells, were recently published in a special issue of Frontiers in Endocrinology: Marine Mammals as Out-of-the-Box Models for Insulin Resistance and Diabetes.

This article was published on pages 16-17 in the January 2014 Nicks n Notches.

Dolphin and stingray interactions

Citizens and tourists of the Sarasota Bay area are well-versed in the “stingray shuffle” to avoid stepping on and being stung by the typically docile, bottom-dwellers found in coastal waters.

But how do stingrays affect bottlenose dolphins?

The Stranding Investigations Program (SIP) at Mote Marine Laboratory provides 24-hour response to stranded marine mammals that are either sick, injured, or dead within the coastal waters of Sarasota and Manatee counties.   The SIP works closely with the Sarasota Dolphin Research Program to identify and recover stranded resident bottlenose dolphins.

Since 1991, 72 resident dolphin have been recovered by the joint programs and upon necropsy (animal autopsy) stingray spines were found in nearly 25% of the dolphins (11 females and 7 males) and suspected in one other case.

How dolphins interact or come into contact with the stingrays is not completely understood.  The stingray barb itself is not always the cause of death, but certainly can contribute to pain and overall poor health.  Often, it is possible to trace the path that the stingray barb took through the dolphin’s body.  The barb generally migrates until it hits something hard, like bone, or the body responds by attempting to wall it off.

In the case of mom, “Jose”, and son, “JOSC”, which are two well-studied Sarasota Bay dolphins typically seen in deep water, both had stingray barbs discovered upon necropsy.  “Jose” stranded on April 12, 2006, emaciated, with a fishing lure in her mouth and a stingray barb that was encapsulated in the right lung.  These findings contributed to “Jose’s” death.  It’s not known if stingray or fishing interaction came first.  The lure would have made it very difficult for “Jose” to hunt and eat, but ultimately, the stingray barb found in the lung was determined to be the cause of death.  For son, “JOSC,” stranded on March 17, 2013, a stingray barb had migrated into the vertebrae, piercing the first vertebra and causing changes to the bones of his skull and surrounding vertebrae. “JOSC” was also emaciated and had severe ulcers in his stomach. As was the case with his mom, “JOSC” died because of the injuries caused by the stingray barb.  These two examples demonstrate how both human and natural factors can harm dolphins and are a good reminder that thorough investigation into the cause of death is important in understanding the threats that these animals face.

This article was published on page 16 in the January 2014 Nicks n Notches.