Saturday, June 23, 2012

When the "lost years" end

Juvenile loggerhead sea turtle being rehabilitated. Photo by author.
Most species of sea turtles - all except flatbacks and leatherbacks - have an oceanic juvenile stage, called the "lost years" between the time they hatch to when the settle as juveniles in near shore, or neritic, habitats. And for a variety of reasons, the coastal waters where juvenile turtles eat and grow are usually not near the nesting beaches where they will breed as adults. And so, after several years, and for most species of sea turtles, decades, the juvenile turtles in neritic habitats become mature and initiate breeding migrations as part of their next stage in the life cycle (Heppell et al. 2003)

Given the large body size reached by this stage in the life cycle, mortality due to natural predation is quite low. That is, these turtles are now too large for most ocean predators to be a real threat. And  turtles have been shown to be highly adapted physiologically to survive environmental fluxes (food availability, water temperature, storms and etc.) by employing various strategies including reserving resources, slowing metabolic processes, entering hibernation-like torpor states, survival within this stage should be quite high (Felger et al. 1976, Heppell et al. 2003). However, survivability during both the juvenile and adult neritic stage of life is largely dependent on exposure to anthropogenic impacts – especially fishing (intentional and incidental take) and pollution (Crouse et al. 1987). This will be a focused on more later.

During breeding migrations, both male and female turtles from multiple foraging grounds migrate and converge on breeding areas near the same beach where they hatched out decades earlier! This is called their "natal beach". Mating occurs in the water near the nesting beaches, and also during migrations – which is one way turtles are thought to increase gene flow among nesting groups. And while variation among species and populations exists, individuals from most species do not breed every year. Instead, female turtles migrate and nest in two to three year cycles, and this is based on tagging and tracking of female turtles. There is still much to be learned about the breeding and behavior of adult male turtles, who are harder to tag and study since they never come ashore the way that the females do to lay their nests. 

Sea turtle nest and female turtle tracks - see the V-shape tracks. Photo by author.
A nesting female sea turtle lay a single nest, or clutch, consisting of 40-100 eggs (depending on species), at each nesting event. Nesting typically occurs during the night. Females may lay multiple clutches during the 1-3 month-long nesting season, and each clutch of eggs has typically been fertilized by more than one male, which is another way to enhancing genetic diversity and maximizing survivability and fitness of offspring (Stewart and Dutton 2011, Hamann et al. 2003). Upon completion of laying the final clutch of eggs, the female turtles, as well as the males who have been gathered offshore, migrate back to their foraging grounds, leaving the nests and the developing hatchlings alone on the beach. 

In 40-60 days (again, depending on species, location, and other environmental factors), the hatchlings will emerge from the nest and begin their own journey through the life cycle. 


Conservatively, a female turtle may start nesting when she is thirty years old, and may continue nesting for 30 to 60 years; therefore, a reproductively mature female who has survived to sexual maturity has a very high reproductive value (Crouse et al. 1987, Heppell et al. 2003). That is to say, a full grown female turtle is very valuable to the continued existence of that sea turtle population.

A handful of nesting site studies range longer than 30 years, including Tortuguero in Costa Rico, Hawaii in the USA, and Michoacán in Mexico, and our understanding of sea turtle reproductive and life expectancy is still in progress. This is also further complicated by the lack of technique to determine the age of a turtle. The age of living sea turtles is still a great unknown. Captive-raised turtles have been known to live for nearly 30+ years (Schwartz 1997, Snover et al. 2007b), but we know turtles live much longer than that. The age of a sea turtle can be estimated based on its size, and after a sea turtle has died, a method called skeletochronology can also estimate age. Skeletochronology is similar to the process used to age trees by cross-section (dendrology) and marine mammals by tooth cross-section (Zug 1985, Zug et al. 1986)

Green sea turtle foraging (eating) in the Caribbean. Photo by author.
Yet to this day, there is no way to accurately age a living wild sea turtle, as a result, age-at-size estimates are most commonly used to study life history and to construct population structure and abundance models (Crouse et al. 1987, Heppell et al. 2003). In 1986, George Zug and colleagues described the process of skeletochronology for sea turtles, and since then, multiple studies have been conduced describing growth and age information for several marine turtle populations using this technique. 

Studies include green turtles Chelonia mydas, in Hawaii (Zug 1985, Zug et al. 2002), and the Caribbean/Atlantic (Goshe et al. 2010, Zug and Glor 1998, Bjorndal et al. 1998), loggerheads Caretta caretta in Gulf of Mexico/Atlantic (Zug et al. 1986, Coles et al. 2001, Snover and Hohn 2004, Snover et al. 2007a, Parham and Zug 1997), and the Mediterranean (Casale et al. 2011) and in the Pacific (Zug et al. 1995), for Kemp’s ridleys Lepidochelys kempii in the Gulf of Mexico (Avens and Goshe 2007, Snover and Hohn 2004, Snover et al. 2007b, Zug et al. 1997), leatherbacks Dermochelys coriacea in the Atlantic (Snover and Rhodin 2008) and olive ridley’s Lepidochelys olivacea in the Pacific (Zug et al. 2006). Similarly, Reich compared skeletochronology of loggerheads and green turtles together with layers of scute material (layers of the sea turtle's shell, or carapace) of green turtles to estimate age at settlement for green turtles in the Atlantic (Reich et al. 2007)

Skeletochronology will be one of two primary techniques I will use for my research, and is what I've been learning all about during my time here in North Carolina.



References:


Avens L, Goshe LR. 2007. Comparative skeletochronological analysis of Kemp's ridley (Lepidochelys kempii) and loggerhead (Caretta caretta) humeri and scleral ossicles. Marine Biology (Berlin) 152(6):1309-1317.
Bjorndal KA, Bolten AB, Bennett RA, Jacobson ER, Wronski TJ, Valeski JJ, Eliazar PJ. 1998. Age and growth in sea turtles: Limitations of skeletochronology for demographic studies. Copeia(1):23-30.
Casale P, Conte N, Freggi D, Cioni C, Argano R. 2011. Age and growth determination by skeletochronology in loggerhead sea turtles (Caretta caretta) from the Mediterranean Sea. Scientia Marina 75(1):197-203.
Coles WC, Musick JA, Williamson LA. 2001. Skeletochronology validation from an adult loggerhead (Caretta caretta). Copeia(1):240-242.
Crouse DT, Crowder LB, Caswell H. 1987. A STAGE-BASED POPULATION MODEL FOR LOGGERHEAD SEA TURTLES AND IMPLICATIONS FOR CONSERVATION. Ecology (Washington D C) 68(5):1412-1423.
Felger RS, Cliffton K, Regal PJ. 1976. WINTER DORMANCY IN SEA TURTLES - INDEPENDENT DISCOVERY AND EXPLOITATION IN GULF OF CALIFORNIA BY 2 LOCAL CULTURES. Science 191(4224):283-285.
Goshe LR, Avens L, Scharf FS, Southwood AL. 2010. Estimation of age at maturation and growth of Atlantic green turtles (Chelonia mydas) using skeletochronology. Marine Biology 157(8):1725-1740.
Hamann M, Limpus CJ, Owens DW. 2003. Reproductive cycles of males and females. The biology of sea turtles. Volume II.:135-161.
Heppell SS, Snover ML, Crowder LB. 2003. Sea turtle population ecology.
Parham JF, Zug GR. 1997. Age and growth of loggerhead sea turtles (Caretta caretta) of coastal Georgia: An assessment of skeletochronological age-estimates. Bulletin of Marine Science 61(2):287-304.
Reich KJ, Bjorndal KA, Bolten AB. 2007. The 'lost years' of green turtles: using stable isotopes to study cryptic lifestages. Biology Letters 3(6):712-714.
Schwartz FJ. 1997. Growth, maturity, and reproduction of a long-term captive male loggerhead sea turtle, Caretta caretta (Chelonia, Reptilia), in North Carolina. Journal of the Elisha Mitchell Scientific Society 113(3):143-148.
Snover ML, Avens L, Hohn AA. 2007a. Back-calculating length from skeletal growth marks in loggerhead sea turtles Caretta caretta. Endangered Species Research 3(1):95-104.
Snover ML, Hohn AA. 2004. Validation and interpretation of annual skeletal marks in loggerhead (Caretta caretta) and Kemp's ridley (Lepidochelys kempii) sea turtles. Fishery Bulletin (Seattle) 102(4):682-692.
Snover ML, Hohn AA, Crowder LB, Heppell SS. 2007b. Age and growth in Kemp's ridley sea turtles: evidence from mark-recapture and skeletochronology.
Snover ML, Rhodin AGJ. 2008. Comparative ontogenetic and phylogenetic aspects of chelonian chondro-osseous growth and skeletochronology. Biology of Turtles:17-43.
Stewart KR, Dutton PH. 2011. Paternal genotype reconstruction reveals multiple paternity and sex ratios in a breeding population of leatherback turtles (Dermochelys coriacea). Conservation Genetics 12(4):1101-1113.
Zug GR. 1985. Skeletochronological age estimates for Hawaiian green turtles. Marine Turtle Newsletter:9-10.
Zug GR, Balazs GH, Wetherall JA. 1995. Growth in juvenile loggerhead sea turtles (Caretta caretta) in the North Pacific pelagic habitat. Copeia 1995(2):484-487.
Zug GR, Balazs GH, Wetherall JA, Parker DM, Murakawa SKK. 2002. Age and growth of Hawaiian green seaturtles (Chelonia mydas): an analysis based on skeletochronology. Fishery Bulletin 100(1):117-127.
Zug GR, Chaloupka M, Balazs GH. 2006. Age and growth in olive ridley seaturtles (Lepidochelys olivacea) from the north-central Pacific: a skeletochronological analysis. Marine Ecology-an Evolutionary Perspective 27(3):263-270.
Zug GR, Glor RE. 1998. Estimates of age and growth in a population of green sea turtles (Chelonia mydas) from the Indian River lagoon system, Florida: a skeletochronological analysis. Canadian Journal of Zoology-Revue Canadienne De Zoologie 76(8):1497-1506.
Zug GR, Kalb HJ, Luzar SJ. 1997. Age and growth in wild Kemp's ridley seaturtles Lepidochelys kempii from skeletochronological data. Biological Conservation 80(3):261-268.
Zug GR, Wynn AH, Ruckdeschel C. 1986. Age determination of loggerhead sea turtles, Caretta caretta, by incremental growth marks in the skeleton. Smithsonian Contributions to Zoology:i.


Wednesday, June 20, 2012

What do we know about young sea turtles' "lost years"?


Archie Carr, sea turtle researcher and conservationist extraordinaire, originally coined the oceanic juvenile stage of young sea turtles the “lost year”. And while Carr learned early that this stage is  actually much longer than a year, the duration of this stage remains one of the great mysteries of these animals’ life history (Carr 1986, Carr 1987, Wallace et al. 2011). (See the previous post for more on turtles' life cycle.)

Where the juveniles are during this stage, what they do, what they eat, and the duration of this stage remains largely unknown for most sea turtle populations. In the Atlantic, juvenile oceanic loggerheads (Caretta caretta), have been most well documented, as they float and forage in Sargassum rafts circulating around the North Atlantic gyre (Bolton 2003). Currently, our best understanding is that juvenile turtles navigate to the water from their nest using visual cues, and once in the water, they move away from shore, at first using wave orientation and then magnetic compass orientation to find offshore ocean currents where they join floating material, typically along convergence zones, and forage opportunistically among mats of algae such as Sargassum and other floating aggregated debris (Lohmann, 1997). Eventually, juvenile turtles of the Chelonia family that have grown large enough shift ontogenetically and settle into nearshore ecosystems to forage during the neritic juvenile stage (Carr 1986, Plotkin 2003). (The single non-Chelonia species, the leatherback, Dermochelys coriacea, is thought to remain pelagic for its entire life.) 
Loggerhead hatchlings in Sargassum. Photo by author.
This life-stage shift, or ontogenetic shift, observed in sea turtles is typical of many marine species. Once the body size of an animal is large enough that the risk of predation in the near shore (neritic) habitat is reduced, this shift allows the animal to maximize its growth by moving to a more productive, high-quality habitat, such as coastal ecosystems (Werner and Gilliam 1984, Seminoff et al. 2002b, Eguchi et al. 2012). Werner and Gilliam’s 1984 review demonstrates this size-driven ontogenetic shift to be a typical transition for aquatic animals with size-structured populations, as is the case with sea turtles.

In these near shore habitats, research on turtles at foraging grounds has provided a good deal of information about this neritic stage of the turtle life cycle. Despite this being a more difficult habitat for researchers to study when compared to research conducted at nesting beaches, turtles foraging neritically are still vastly more accessible than migrating or oceanic foraging turtles. Neritic juvenile turtles, now large enough to be at a lower risk of predation by coastal marine predators, feed on a more reliable supply of food, in water that is often warmer than open ocean water, and where animals are able find and consume food much more efficiently. These factors can allow turtles to grow more rapidly as their energy expenditure and handling time is reduced and food quality and metabolism is increased (Seminoff et al. 2002b, Seminoff et al. 2003, Eguchi et al. 2012, Snover et al. 2010). Balancing the tradeoff between maximizing growth rate with minimizing predation, whereby the ratio of mortality to growth rate is minimized, drives the mechanism of this early life history strategy. In many instances, this is directly correlated to body size, as has been shown to among several species, particularly animals in aquatic systems (Werner and Gilliam 1984, Werner and Anholt 1993, Brooks and Dodson 1965). The timing of this ontogenetic shift and the duration of the pelagic juvenile stage leading up to this habitat shift are two primary focuses of my research.

So, in order to try to and learn more about this stage of life, for two populations of sea turtles - the East Pacific green turtles and the North Pacific loggerheads - here I am, in North Carolina, learning from experts at the NOAA NMFS Southeast Science Center's Sea Turtle Aging Laboratory! More about what I've learned so far, coming up next!


References:

Brooks JL, Dodson SI. 1965. PREDATION BODY SIZE AND COMPOSITION OF PLANKTON. Science 150(3692):28-&.
Carr A. 1986. RIPS, FADS, AND LITTLE LOGGERHEADS. Bioscience 36(2):92-100.
Carr A. 1987. NEW PERSPECTIVES ON THE PELAGIC STAGE OF SEA TURTLE DEVELOPMENT. Conservation Biology 1(2):103-121.
Crouse DT, Crowder LB, Caswell H. 1987. A STAGE-BASED POPULATION MODEL FOR LOGGERHEAD SEA TURTLES AND IMPLICATIONS FOR CONSERVATION. Ecology (Washington D C) 68(5):1412-1423.
Eguchi T, Seminoff JA, LeRoux RA, Prosperi D, Dutton DL, Dutton PH. 2012. MORPHOLOGY AND GROWTH RATES OF THE GREEN SEA TURTLE (CHELONIA MYDAS) IN A NORTHERN-MOST TEMPERATE FORAGING GROUND. Herpetologica 68(1):76-87.
Felger RS, Cliffton K, Regal PJ. 1976. WINTER DORMANCY IN SEA TURTLES - INDEPENDENT DISCOVERY AND EXPLOITATION IN GULF OF CALIFORNIA BY 2 LOCAL CULTURES. Science 191(4224):283-285.
Hamann M, Limpus CJ, Owens DW. 2003. Reproductive cycles of males and females. The biology of sea turtles. Volume II.:135-161.
Heppell SS, Snover ML, Crowder LB. 2003. Sea turtle population ecology.
Plotkin P. 2003. Adult migrations and habitat use. The biology of sea turtles. Volume II.:225-241.
Seminoff JA, Jones TT, Resendiz A, Nichols WJ, Chaloupka MY. 2003. Monitoring green turtles (Chelonia mydas) at a coastal foraging area in Baja California, Mexico: multiple indices to describe population status. Journal of the Marine Biological Association of the United Kingdom 83(6):1355-1362.
Seminoff JA, Resendiz A, Nichols WJ, Jones TT. 2002. Growth rates of wild green turtles (Chelonia mydas) at a temperate foraging area in the Gulf of California, Mexico. Copeia(3):610-617.
Snover ML, Hohn AA, Crowder LB, Macko SA. 2010. Combining stable isotopes and skeletal growth marks to detect habitat shifts in juvenile loggerhead sea turtles Caretta caretta. Endangered Species Research 13(1):25-31.
Stewart KR, Dutton PH. 2011. Paternal genotype reconstruction reveals multiple paternity and sex ratios in a breeding population of leatherback turtles (Dermochelys coriacea). Conservation Genetics 12(4):1101-1113.
Wallace BP, DiMatteo AD, Bolten AB, Chaloupka MY, Hutchinson BJ, Abreu-Grobois FA, Mortimer JA, Seminoff JA, Amorocho D, Bjorndal KA et al. . 2011. Global Conservation Priorities for Marine Turtles. Plos One 6(9).
Werner EE, Anholt BR. 1993. ECOLOGICAL CONSEQUENCES OF THE TRADE-OFF BETWEEN GROWTH AND MORTALITY-RATES MEDIATED BY FORAGING ACTIVITY. American Naturalist 142(2):242-272.
Werner EE, Gilliam JF. 1984. THE ONTOGENETIC NICHE AND SPECIES INTERACTIONS IN SIZE STRUCTURED POPULATIONS. Annual Review of Ecology and Systematics 15:393-425.



Thursday, June 14, 2012

First, a bit of background


 General biology and ecology of sea turtles

Image of Archelon skeleton (1902) Yale Peabody Museum 
Since the Cretaceous period, over 100 million years ago, marine turtles have survived throughout the world’s oceans. Fossil records show how ancestors of today’s sea turtles moved from land to water and adapted to their marine environment (Pritchard, 1997). Over time, their bodies took on a flattened shape and their forelimbs elongated and flattened into graceful paddles while their rear legs shortened and spread to become rudder-like appendages well suited for their nearly exclusively aquatic existence. Sea turtles forage at sea on both pelagic (in the water column) and benthic (on the ocean floor) prey, and they also mate at sea, breath air at the ocean’s surface, expel excess salt through specialized glands, and navigate entire ocean basins with extraordinary instinctive mechanisms. Well adapted to the water world, a significant remnant of their terrestrial ancestry remains, however, as they remain tied to the land for their final stage of reproduction. 


Turtle nesting beach near Juno Beach, FL. Image by author.
Adult female turtles nest on beaches, the same beaches where they themselves were born as hatchlings decades earlier. And so, despite turtles’ nearly complete transition from land to water, as fellow marine tetrapods such as the cetaceans like whales and dolphins have successfully done, sea turtles’ complex life history spans multiple marine ecosystems including land and sea. Tested by time, this strategy has enabled seven species of extant sea turtles to continue to persist worldwide. Yet the existence of all seven species is at risk, and a multitude of local and international efforts and policies now exist to help protect the remaining sea turtle populations across the globe. During past geologic periods, stochastic factors such as dinosaurs, meteorites, drifting continents, drastic climate shifts including ice ages, threatened all sea turtle species and eliminated most of them. Yet today, the perilous state of those ancient species that were able to survive is primarily due to human activities such as exploitation (harvesting of animals and eggs) and habitat destruction and (degradation and elimination of nesting beaches and foraging grounds) (Milton and Lutz 2003, Campbell 2003).

Utilized, honored, and observed for millennia by cultures worldwide (Frazier 2003) scientists of the past century have studied these long-lived, slow growing, migratory animals to learn how and where sea turtles live and to attempt to unravel the mysteries of these animals’ complex life history. Working in a collaborative atmosphere, scientists have elucidated some of the most critical and fascinating aspects of sea turtle biology and ecology. And yet despite all this work, much remains to be understood with regards to the complex life history and basic biology of these beloved and charismatic marine vertebrates (Wallace et al. 2011).

Complex life history

Image from: Sea Turtle Foundation website, available at: http://www.seaturtlefoundation.org
Sea turtles live upwards of 100 years and during this lifespan they inhabit a diverse variety of marine ecosystems. Developing sea turtles move through a complex life history during which they undergo multiple changes, called ontogenetic habitat shifts. This basic life history of marine turtles begins with hatchlings emerging from nests laid by mature females on what is presumed to also be the nesting mother’s natal beach (where she was born). Upon emergence, the hatchlings scramble in a frenzy across the beach toward the ocean, through the breaking waves and out to the currents of the open ocean. While survivability in this initial stage varies among species, deterministic and stochastic factors such as nest location, season and individual nesting female, hatch-success rates is typically around 80% (Miller, 1997). However, as the hatchlings transition from the safety of the nest to the deeper ocean waters, mortality rates increase, as predators are many and the environment is harsh. 

Loggerhead hatching in sargassum. Image by author.
Those hatchlings who avoid the predators of the nests (i.e. ghost crabs, ants, beetles, bacteria, dogs, pigs, coatis, people & etc.), the beach (crabs, gulls, dogs & etc.) and coastal waters (fish, seabirds, crabs & etc.) and are able to withstand the drying intensity of the sun, distracting light pollution, navigate around natural and anthropogenic debris (humans' trash) and find the ocean eventually begin the oceanic juvenile stage of the sea turtle life cycle. Survivorship in the coastal (neritic) habitats is low for hatchlings, and hatchlings of all species move to oceanic habitats immediately, where risk of predation is lower. An exception to this pattern is Australia’s flatback sea turtle (Natator depressus), which remains neritic its entire life. Flatback hatchlings are nearly twice as large as hatchlings of other cheloniid species (~6 inches vs. ~3 inches), showing selection for immediate neritic settlement (Limpus et al. 1983, Walker and Parmenter 1990). Archie Carr originally coined this stage of the pelagic juveniles the “lost year”. And while this stage is now known to be much longer than a year, it remains one of the great mysteries of these animals’ life history (Carr 1986, Carr 1987, Wallace et al. 2011).

Where the juveniles are during this stage, what they do, what they eat, and the duration of this stage remains largely unknown for most sea turtle populations.This is the focus of my research, and will be the focus of the next post.



References:
Campbell, L. (2003) ‘Contemporary Culture, Use, and Conservation of Sea Turtles’, The
            Biology of Sea Turtles, Volume II. 307-338.
Carr A. 1986. RIPS, FADS, AND LITTLE LOGGERHEADS. Bioscience 36(2):92-100.
Carr A. 1987. NEW PERSPECTIVES ON THE PELAGIC STAGE OF SEA TURTLE DEVELOPMENT. Conservation Biology 1(2):103-121.
Frazier J. 2003. Prehistoric and ancient historic interactions between humans and marine turtles. The biology of sea turtles. Volume II.:1-38.
Limpus CJ, Parmenter CJ, Baker V, Fleay A. 1983. THE FLATBACK TURTLE CHELONIA-DEPRESSA IN QUEENSLAND AUSTRALIA POST NESTING MIGRATION AND FEEDING GROUND DISTRIBUTION. Australian Wildlife Research 10(3):557-562.
Miller, J. (1997) ‘Reproduction in Sea Turtles’, The Biology of Sea Turtles, Volume 1.,
            51-81.
Milton, S. and, Lutz, P. (2003) ‘Physiological and Genetic Responses to Environmental
            Stress’, The Biology of Sea Turtles, Volume II. 163-197.
 Pritchard, P. (1997) ‘Evolution, Phylogeny, and Current Status’, The Biology of Sea
Turtles, Volume 1., 1-28.
 Walker TA, Parmenter CJ. 1990. ABSENCE OF A PELAGIC PHASE IN THE LIFE-CYCLE OF THE FLATBACK TURTLE, NATATOR-DEPRESSA (GARMAN). Journal of Biogeography 17(3):275-278.
Wallace BP, DiMatteo AD, Bolten AB, Chaloupka MY, Hutchinson BJ, Abreu-Grobois FA, Mortimer JA, Seminoff JA, Amorocho D, Bjorndal KA et al. . 2011. Global Conservation Priorities for Marine Turtles. Plos One 6(9).
 

Tuesday, June 12, 2012

Year End Update

As readers may know, I'm wrapping up my first year in my PhD program at UCSD in marine ecology where I am studying two species of sea turtles, green (Chelonia mydas) and loggerheads (Caretta caretta), that live in the Pacific ocean. Specifically, I'm looking at a particular stage of the turtles' lives, the years following hatching which are essentially the childhood and teenage years of these turtles. 

Both of these species of sea turtles are found across the globe, and so in order to better protect and study such widespread animals, specific groups of these species are separated depending on where they live. So, my work focuses on the group of East Pacific green sea turtles which typically range from southern Mexico, to southern California; and the North Pacific loggerhead sea turtles which typically range from Japan (where they are born), across the Central Pacific (near Hawaii), to Baja California, Mexico.


After a year of course work at UCSD and learning preliminary techniques at NOAA's Southwest Fisheries labs in La Jolla, California, all of which I will use to address my key research questions, I am now in North Carolina being trained at NOAA's Southeast Fisheries Sea Turtle Aging Laboratory! A series of upcoming posts will explain a bit more background on sea turtles, these two populations I'm studying, the questions I'll be addressing in my research, and finally take readers on the journey as I conduct my research.


As a final wrap up - this year's monitoring of our resident San Diego Sea Turtles in the San Diego Bay finished up for the year a couple of weeks ago.  Altogether it was another successful and fun-filled season on the Bay! It has now been almost two years since the South Bay Power Plant shut down, and as predicted by scientists studying this population, the turtles are still here. It is true, that the turtles do seem to be visiting slightly different parts of the South San Diego Bay for different amounts of time and at slightly different times of day and times of year - but the turtles are most definitely still in the south part of the bay, and ongoing research is helping us learn more are more about these turtles, their behavior, and their overall status.  

Finally, to answer a recent question: No, we still haven's seen Wrinklebutt... she continues to elude us. But, we did find another very, very large female turtle this year. She is likely the second largest we've encountered on our surveys, next to Wrinklebutt! This big lady we captured was enormous, it took four of us to pull her into our boat (two or three people is usually plenty!). She weighed about 190 kilos, which is nearly 420 pounds! And while most turtles we work with are quiet, and the only sound you hear from them is their deep breathing, this gal was loud and very audible - she made an almost hissing sound as we pulled her in the boat. It was quite the adventure- and it was a very fun day as a sea turtle ecologist!