Turtles Flashcards
When did reptiles first appear?
~320 million years ago during the Carboniferous.
(Vitt & Caldwell, 2014 pg.3)
What are the clades of reptiles?
Archosauria (crocodylians and birds)
Testudines (turtles)
Lepidosauria (tuataras and squamates)
(Vitt & Caldwell, 2014 pg.5)
What is a turtle?
An ectothermic animal, specifically a reptile, that is a toothless, vertebrate with four feet (tetrapod) that reproduces by depositing eggs (oviparity), whose body is encased within a shell made of bone that protects it.
(Vitt & Caldwell, 2014)
What did tetrapods descend from and how?
Lobe-finned fishes.
Strong pectoral fins gradually evolved into limbs.
(Vitt & Caldwell, 2014 pg.8)
What is the taxonomy for turtles?
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Subphylum: Vetebrata
Tetrapoda
Amphibia
Amniota
Class: Reptilia
Order: Testudines
What has the greatest impacts on the development of turtle eggs?
Temperature
Water availability
Gas exchange
(Vitt & Caldwell, 2014 pg.42)
What are the impacts of temperature on reptile egg development? How else for turtles specifically?
Too low = development can’t take place as quickly as it needs to so they don’t hatch on time and can emerge when conditions aren’t great.
Too high = they use up all the resources within the egg before completely developing.
(Vitt & Caldwell, 2014 pg.42)
For most turtles, sex is determined by temperatures present during egg development with warmer temperatures usually producing females.
(Ernst and Lovich 2009)
What are the impacts of moisture on reptile egg development?
Too much or too little = poor gas exchange impeding development.
(Vitt & Caldwell, 2014 pg.43)
How does a turtle monitor its environment? What do they use?
Sense organs.
Skin (cutaneous sense organs):
Pain and temperature receptors
Mechanoreceptors for pressure and touch (e.g., tension, stretching).
Ears:
Neuromasts in inner ear - Hearing, balance, position and movement of head.
Eyes:
Retina - light
Nose (nasal organs):
Vestibule (nasal cavity) lined with sensory or olfactory epithelium.
Internal sense organs:
Proprioceptor organs - tension and stress on musculoskeletal system
Taste buds
(Vitt & Caldwell, 2014 pg.68-71)
How long have turtles been around?
At least 220-210 million years - Late Triassic.
(Vitt & Caldwell, 2014 pg.105)
How big was the biggest turtle recorded? When?
Carapace length of 3m.
Miocene
(Vitt & Caldwell, 2014 pg.106)
For reptiles, when is mortality often the greatest?
When they’re eggs.
(Vitt & Caldwell, 2014 pg.125)
What is the general life history of all turtles?
Mature later in life,
reproduce for many years,
are long-lived,
have 3 life stages: egg, juvenile, adult,
Reproduce by internal fertilization,
then oviparity (lay eggs).
(Vitt & Caldwell, 2014 pg.150)
What are some factors that impact a reptile’s home range?
Sex
Animal size
Population density
Resource availability
Microclimate
Physical structure of habitat
Energy requirements
(Vitt & Caldwell, 2014 pg.232,235, 237)
How do turtles maintain buoyancy?
By adjusting the amount of air in their lungs and the amount of water in their cloacal bursa.
(Jackson, 2011)
What does basking do to a turtle?
It increases the rate of chemical reactions within the turtle and subsequently its metabolism.
It also lowers the pH level and increases the CO2 level of the turtle’s blood.
(Jackson, 2011)
Where do turtles fit in the food web?
As a group, turtles occupy trophic positions as herbivores, carnivores, and omnivores and play important, even dominant, roles in their communities, sometimes as a top predator.
(Lovich et al, 2018)
Why are turtles important?
- They normally (pre-humans) contribute a lot of biomass meaning they have a large impact on the ecosystem just because of how many of them are normally present.
- Contribute to energy flow in their immediate and surrounding environment.
(e.g., eggs = flow from aquatic to terrestrial via predation and into soils, as consumers they remove carrion) - Contribute to mineral cycling.
(e.g., lots of Ca in their bones that goes into habitat when they die) - Environmental indicators - long-lived so accumulate toxins.
- Important members of food web and their removal can cause trophic cascades.
- Important agents for seed dispersal and germination enhancement.
- Important in bioturbation by contributing to soil processes including its formation, function, and maintenance.
- The ability of some turtles to survive in polluted waterways could potentially make them useful for restoration.
- They are culturally important both as food and spiritually.
(Ernst and Lovich, 2009; Lovich et al, 2018)
Why is it especially sad that turtles are so threatened?
Turtles are an ancient group going back over 200 million years - they predate mammals and birds and outlived the dinosaurs.
Showing they’ve been able to outlive tons of things thrown at them, yet can’t survive modern humans.
(Lovich et al, 2018)
Why are turtles so threatened?
- A global focus by conservation programs to prioritize and target areas that protect birds and mammals but do not adequately consider turtle diversity….ok for turtles with larger ranges but not smaller ones.
- Habitat loss and degradation
(e.g., forest loss, agriculture, water quality, hardening of shorelines, removal of logs/basking/prey sites) - Disease
- Over-collection of turtles and their eggs for food consumption and the international pet trade, as well as over-collection for the trade in traditional medicines made from turtle parts
- Climate change (many turtles have environmental sex determination)
- Invasive species
(e.g., severely increased egg predation by invasive predators) - Pollution
(Ernst and Lovich, 2009; Cox et al, 2022; Lovich et al, 2018; Stanford et al, 2020)
How can further turtle extinctions be prevented?
Protect remaining habitat, especially 16 hotspots.
Lower consumption of turtles and eggs including bycatch.
Captive breeding and reintroductions.
Enforcement of new and existing laws.
More research.
Engage locals.
(Stanford et al, 2020)
Describe how life history traits relate to catastrophic events.
How does this relate to turtles?
Provide example.
Populations with faster life histories are more vulnerable to perturbations in reproductive success, whereas those with slow life histories are most sensitive to adult survivorship and thus take longer to recover from depletion.
Turtles typify the slow end of the life-history spectrum, exhibiting iteroparity, high adult survivorship, and low and variable juvenile recruitment. Populations of organisms with slow life-history strategies are vulnerable to even small decreases in adult survivorship, with as little as a 2–3% reduction in survivorship resulting in severe population decline.
e.g., 23 year study done by Mathew Keevil & others in 2018 on snapping turtles in Algonquin park after predation catastrophe showed that
their survivorship was the same before the incident but their abundances did not increase after the catastrophe even though it was a long enough timeframe that offspring after the catastrophe would have been recruited. They estimated it could take 59 years to see any recovery.
(Keevil et al, 2018)
What is an advantage of long life histories in turtles?
The life history of turtles is typified by low and variable reproductive success and their strategy of constant, high adult survivorship insulates the population from routine environmental stochasticity which primarily affects the youngest age classes.
(Keevil et al, 2018)
How are turtle nests identified?
After the female leaves the nest, two mounds of dirt with an imprint of the tail in the centre remain, forming an “arrow” that points to the eggs in the nest chamber.
(Congdon et al, 2008)
What are some stressors for turtles?
Overcrowding
Extreme temperatures
Nutritional deficiency
Sudden exposure to different temperatures
Removal from natural conditions
(Mahmoud & Akindi, 2008)
How does temperature influence turtle sex?
Consistently low temperatures produces males, whereas consistently high temperatures produce females.
(Spotilla & Bell, 2008)
