Turtles: a cause for wonder,
a cause for concern
Thomas Akre
Longwood University
Farmville, VA
The Tortoise and the Hare
Turtles: a cause for wonder
• "Because they are still living, turtles are
commonplace objects to us: were they entirely
extinct, their shells – the most remarkable
defensive armor ever assumed by a tetrapod –
would be a cause for wonder."
Alfred Sherwood Romer (1894–1973)
Remarkable Defensive Armor
E. S. Gaffney.
Survivors in Armor
• Turtles (Order Testudines) are a unique
(monophyletic) and highly divergent lineage
• They have existed nearly unchanged for at
least 210 million years and survived the last
great mass extinction 65 mya
Survivors in Armor
All Genera
Well-defined Genera
Mass Extinctions
Triassic
Millions of years ago
Thousands of Genera
Survivors in Armor
Survivors in Armor
All Genera
Well-defined Genera
Mass Extinctions
Millions of years ago
Cretaceous “K-T”
Thousands of Genera
Survivors in Armor
Turtles in the Tree of Life
Laurin & Gauthier 2009
Turtle Relatives - Procolophonids
Nycteroleter
D. Bogdanov
Turtle Relatives - Pareiasaurs
E. Karkemish
Turtles in the Tree of Life
Modesto & Anderson 2004
Turtle Relatives - Plesiosaurs
Thalassiodracon hawkinsi
N. Tamura
The First Turtle?
Odontochelys semitestacea
Li et al. 2008
M. Donnelly
The Earliest Turtles
Proganochelys quenstedti
C. Houck
Li et al. 2008
The Turtle Tree of Life
Odontochelys
Joyce & Gauthier 2004
Species Richness
Tortoise and Freshwater Turtle Species Richness by
12100 km2 Grid
The Side-Neck Turtles
Gaffney and Meylan 1988
How to Protect Your Neck
F. Ippolito.
Pleurodire
Cryptodire
The Side-Neck Turtles
• Pleurodires
Global Diversification
Tortoise and Freshwater Turtle Mean Root
Distance by 12100 km2 Grid
Renous et al. 2008
Meiolania: the Horned Turtle
Gaffney and Meylan 1988
Meiolania: Survivors in Armor
Meiolania platyceps
F. Ippolito.
C. Houck
Oceanic Voyages
Gerlach et al. 2006
So what is a turtle and what does it
mean to be a turtle?
• In general, turtles have a suite of co-evolved
life history characteristics that make them
vulnerable to the effects of human
encroachment
• Life history theory and evidence from longterm population studies suggest that turtles
live so long because they are bet-hedgers;
they have adapted to environments with
unpredictable juvenile survivorship
General Model of Turtle Life-History
Traits
•
•
•
•
•
•
•
•
Low nest (clutch) survivorship
Low, but variable juvenile survivorship
Delayed sexual maturity (4–30 yrs)
At a certain size the shell confers protection that
leads to high adult survivorship (often > 95%)
Low annual reproductive output (fecundity)
Repeated reproductive cycles (extreme iteroparity)
Long life-span (mean max. from 15–200 yrs)
Reduced or non-existent senescence
Delayed Maturity
Loxodonta africana
Glyptemys muhlenbergii
A. Teti
The Whale in the Turtle
Dermochelys coriacea
C. Safina
“Mammalian” Bone Growth
Wyneken et al. 2008
Giant Turtles
Archelon ischryos
Stupendemys geographicus
R. Somma
F. A. Lucas
Survival
The Tongue of the Turtle
Heiss et al. 2010
The Fish in the Turtle
Feeding
A Buffer Against the Cold
Temperature Dependent Sex
Determination and Female Choice
Chrysemys picta
M. Marchand
M. Jones
Cann 1998
Nest Site Selection & Diapause
Diapause and Aestivation
Longevity
Reproduction & Longevity
• Indeterminant Growth and Experience
Reproductive output,
Nest Success &
Hatchling survivorship
Cost of reproduction
Turtles: a cause for concern
• "Because they are still living, turtles are
commonplace objects to us: were they
entirely extinct, their shells – the most
remarkable defensive armor ever assumed by
a tetrapod – would be a cause for wonder."
Alfred Sherwood Romer (1894–1973)
There is a
Global Turtle Survival Crisis
Disease
Habitat Loss
Unsustainable Use
Global Turtle Survival Crisis
Global Climate Change
Pollution
Invasive species
Primary feeder
markets of
turtle
imports into
China…
…have now
reached into
India, New
Guinea, Africa,
and the United
States
IUCN RED LIST CATEGORY STATUS FOR THE
WORLDS 265+ TURTLES
2 2
23
Extinct
74
48
Extinct in Wild
Critically Endangered
Endangered
Vulnerable
Lower Risk
12
Data Deficient
Not Evaluated
42
62
Nearly half (42%) of the world’s tortoise and
freshwater turtle species are threatened with
extinction
At least 70 species (± 25%) are poised on the brink
of extinction
Discoveries, rediscoveries, and
elevations
Discoveries, rediscoveries, and
elevations
Turtle Services
• They occupy a diverse array of ecological
niches and many species are considered to be
critical components of the ecosystems they
inhabit
M. Dorcas
D. Scott
R. Masroor
Turtle Symbols
Global Species Richness and Turtle
Hotspots
Tortoise and Freshwater Turtle Species Richness by
12100 km2 Grid
Turtle Hotspots and Priority Areas
Ganges-Brahmaputra Basin of India and Bangladesh
The Human Footprint
Turtle Priority Areas
58 species of five families in North America
The Tortoise and the Hare
Thank you
