Sea Turtle Diving Patterns

Green Sea Turtle

Green Sea Turtles (Chelonia mydas) live in coastal waters in tropical and subtropical areas.  Their name comes from the color of their skin, which is an olive green.  They can reach lengths of 5 feet, can weigh up to 700 pounds and live up to 80 years in the wild.  Unlike most sea turtles, they are herbivores and mainly feed on sea grasses and algae.  They are an endangered species, declining in number because of human hunting, boat propeller accidents, and accidental fish net drowning.  Like most turtle species, Green Sea Turtles will dive to different depths of the ocean.  They can stay under water for up to 5 hours and their heart rate can slow to one beat for every 9 minutes.  Diving patterns of sea turtles are unique to each species and scientists have been conducting experiments that focus on the diving patterns of turtles, Green Sea Turtles included.  Knowing more about sea turtle diving patterns can help people understand how to conserve them better and to stop their population declines.

 

One study followed three Green Sea Turtles, two males and one female, during their migrations.  All three of them showed diurnal diving patterns.  They would do shallow, short dives during the day; only going down about 4 meters and staying under for a maximum of 18 minutes.  Around 7pm each night, they would start to dive deeper and for longer periods of time.  On average the dives were 45 feet and they stayed down there for 40 minutes or so.

In another study, the diving patterns in 2004 and 2005 of 5 Green Sea Turtles were observed and compared.  They found that U dives (deep dives) were more common at night than during the day, but there were still some U dives during the day.  This matches up with previous studies that have suggested that sea turtles are more active during the day and rest at night.  The average depths of those dives were between 16 and 20 meters for 2004, while in 2005 the average depths were between 10 and 13 meters.  When the turtles were nearing their nesting grounds, they had fewer U dives and stayed more towards the surface.  

The more time and energy efficient depth to travel at for sea turtles is between 1.5 and 4 meters, so why were the turtles diving so deep at night?  What purpose does that serve them?  Scientists have come up with many possible solutions but none of them have been proven.  Do they dive to avoid predators?  To check for shallow water?  Are the deep dives ‘resting dives’?  Is there a source of food at that depth?  Is it because they want to be in cooler water?  These questions have yet to be answered.

Article References

• http://journals.ohiolink.edu/ejc/pdf.cgi/Rice_Marc_R.pdf?issn=00220981&issue=v356i1-2&article=121_dbothgtmdom
• http://journals.ohiolink.edu/ejc/pdf.cgi/I-Jiunn_C.pdf?issn=00220981&issue=v381i0001&article=18_cidbdtipbgt
• http://journals.ohiolink.edu/ejc/pdf.cgi/Hochscheid_S.pdf?issn=00220981&issue=v450inone_c&article=118_wwmstuotsodb

 Website References

• http://animals.nationalgeographic.com/animals/reptiles/green-turtle/
•  http://marinebio.org/species.asp?id=51

Manatees No Longer Considered Endangered

Cassandra Craig

As of January 2016 manatees were no longer considered an endangered species. “The U.S. Fish and Wildlife Service said on Jan. 7 that Florida's manatee population has recovered enough that the species no longer meets the definition of "endangered" under the Endangered Species Act” (Huffington Post).  The U.S Fish and Wildlife service considered relisting the manatees as “threatened” which wouldn’t change any current protections for them. Based on the best scientific technology available the wildlife service thought it was best to move them off the endangered because they were no longer in danger of becoming extinct. 

When an animal is listed as endangered it means that that species is in imminent risk of extinction while threatened means they could be come endangered in a foreseeable future. The Florida manatee population has grown from the hundreds in 1967 to more than 6,000 counted last year in a statewide survey, which is a 500% increase. If they were to relist the manatees as a threatened species they would be ignoring the ongoing threats to their survival.

 The biggest threats to manatees in the US are boats, cold water, toxic algae blooms, pollution, and fishing nets (Huffington Post).  In other regions they are threatened by significant habitat loss.  There needs to be a viable plan set up for reducing the threats from boats and for preserving a warm water habitat before down listing the Manatees to threatened. 

A Florida business group and the conservative Pacific Foundation want to reclassify the manatees to threatened because they think the population is still recovering.  From 2010-2013 Manatees suffered huge losses from the cold water and the toxic algae blooms. The Manatee still remains protected under the Marine Mammal Protection Act and a 90-day comment period began in January for the public to submit scientific feedback to help reach a decision on what to do. If the ne classification is approved it will not take affect until 2017. Even though Manatees are no longer endangered there still is a lot of work to be done.

http://www.huffingtonpost.com/entry/manatees-no-longer-facing-extinction-but-theres-still-work-to-be-done-to-protect-them_us_5696b862e4b0ce4964230846

Adoption in California Sea Lions

Ever since I swam with a sea lion in Key Largo, FL, I have been interested in learning more about these amazing creatures. They are highly intelligent, can be trained to do tricks in captivity for entertainment, and have even been trained to assist the U.S. navy with their in water needs.

One study on the California sea lion populations was used to provide evidence of adoption by adult female sea lions. This adoption behavior by the females is called alloparental behavior. Pups were captured at two different locations, San Jorge and Los Islotes Islands, where their measurements were recorded, DNA was taken in the form of toe clippings, and they received haircuts and flipper tags for identification. These pups ranged from 4 days to 8 weeks old, and when an adult female was seen nursing one of the tagged pups, a biopsy was performed on her to identify the amount of similarity between the genetic analyses of the female-pup pair. If there were more than one mismatch of the 14 loci being examined, it was determined that the female-pup pair was non-filial, meaning the pup was not the offspring of the female, indicating adoption. In situations where only one mismatch was observed, the pair was concluded as filial due to the fact that there could have been an error in the genotyping of the tissue samples. To reduce these errors, the PCR procedures were repeated for each sample. Additionally, the researchers looked at the effect the adoption of sea lion pups has on population viability, and they modeled different scenarios of how different factors of pup adoption could affect population growth.

A total of 15 female-pup pairs out of the 160 pairs sampled from both locations were identified as relationships that had been formed as the result of adoptions. One case that was not included in these recorded female-pup pairs because it was not randomly sampled was that of a female who was observed calling her pup with no response for three days. The next two months, the same female was observed nursing a tagged pup. The genetic relatedness of the random female-pup pairs, the non-filial pairs, and the filial pairs were calculated for both location and were recorded in the graph below.

 The results of the genetic analyses show that the filial pairs of both locations had a mean r-value of approximately .5, while the r-value of the random and non-filial pairs had means of roughly zero and did not significantly differ between each other. The error bars of the filial groups did not overlap with the random and non-filial groups, indicating that there was a distinct difference between the genetic relatedness of the two. This shows that there was little error in the identification of the filial female-pup pairs.

The adoption of the abandoned pups by adult females increases the population viability by reducing the mortality rates of the pups. Also, as long as their are no reproductive costs to the female, the growth of the population will increase because she may still produce her own offspring as well, increasing the population size. As the results from this experiment are rather broad when determining different effects of alloparenting on the population, this is an aspect that needs to be explored further in future experiments.

This research was important as it was the first form of evidence for adoption in California sea lions, and it can be used to expand upon the subject further. The methods used in this article allowed for an informative data analysis regarding genetics and behavior, and I would like to participate in research similar to this in my career by uncovering different behavioral characteristics of marine mammals.    

Reference:

First Evidence for Adoption in California Sea Lions

Sperm Whale Fall Ecosystems

When we think of whales we typically think of these giant, majestic creatures swimming through the oceans.  These animals play a major role ecologically while alive, but they also play a significant role ecologically when they die.  As their carcass reaches the ocean floor, it provides many species with a unique habitat that allows them to flourish.

An example of a whale fall carcass (from Google images).

One study researched this idea of “whale fall ecosystems.”  A team of researchers looked at the role that sperm whale carcasses play in creating these ecosystems.  Sperm whales were used because they have an oil-rich structure known as the spermaceti organ that the researchers thought would allow for a unique habitat.  In 2002, a stranding of 12 sperm whale carcasses was discovered.  These 12 sperm whales were sunk by local government authorities using barges in the waters of Cape Nomamisaki at depths of 200-300m.  The whales had decomposed internally but maintained most of their external morphology.  Each whale was wrapped in a nylon net.

Only 5 of the whales were studied using a remotely operated vehicle (ROV) with a total of 27 dives made between the years 2003-2005.  Certain bones were collected to identify the species living on them.  Epifaunal species were collected using a suction sampler and infaunal organisms were collected using a scoop sampler.  The paper presents three tables that identify the presence of different species of mollusks, polychaetes and crustaceans on the whale carcasses. 

A. pacifica. (from Google images)

The most abundant species of mollusk found on the whale carcasses was a bivalve known as Adipicola pacifica.  According to the researchers, this species coated the exposed bone while another species of mollusk, Adipicola crypta, preferred the bone that was buried beneath the sediment.  The most abundant gastropod was Dillwynella vitrea.  Polychaetes found in small pores of the whale bone were typically in the Nereididae, Capitellidae and Dorvilleidae families.  Some cirripeds (crustaceans) known as Heteralepas were found on the nets that wrapped the carcasses but not on neighboring rocks, indicating that they preferred the whale carcass.

The shell sizes of the two most abundant mollusks, A. pacifica and A. crypta, were compared.  The shell size of A. pacifica was the largest on the 1.5 year old whale carcasses and gradually decreased through the years.  The shell size of A. crypta was the smallest on the 1.5 year old carcasses and gradually increased.  This should have been an indicator of a “reef stage” of the carcasses according to the researchers, but it seems this was not really observed.

This study proved that a sperm whale carcass can sustain a working ecosystem for more than three years.  Similar studies have been reported on baleen whales, which indicated roughly the same amount of time as these sperm whales.  The organisms found on the sperm whales were similar to those found on the baleen whales at the family level, but not at the species level.

Whales are my favorite animal, and while I prefer the live ones, this study proves their importance even in their afterlife and further strengthens my passion for this animal.

Source: http://proxy.ashland.edu:2315/ehost/pdfviewer/pdfviewer?sid=ce5eb36f-7e78-4ec4-a481-4e989bb07ca4%40sessionmgr120&vid=4&hid=107

Entitled: "Three-year investigations into sperm whale-fall ecosystems in Japan"