Turtles: a cause for wonder, a cause for concern

Thomas AkreLongwood 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

Millions of years ago Thousands of Genera

All GeneraWell-defined Genera

Mass Extinctions

Triassic

Survivors in Armor

Survivors in Armor

Millions of years ago Thousands of Genera

All GeneraWell-defined Genera

Mass ExtinctionsCretaceous “K-T”

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?

Li et al. 2008

Odontochelys semitestacea

M. Donnelly

The Earliest Turtles

Li et al. 2008C. Houck

Proganochelys quenstedti

The Turtle Tree of Life

Joyce & Gauthier 2004

Odontochelys

Tortoise and Freshwater Turtle Species Richness by 12100 km2 Grid

Species Richness

The Side-Neck Turtles

Gaffney and Meylan 1988

How to Protect Your Neck

PleurodireF. Ippolito.

Cryptodire

The Side-Neck Turtles• Pleurodires

Tortoise and Freshwater Turtle Mean Root Distance by 12100 km2 Grid

Global Diversification

Renous et al. 2008

Meiolania: the Horned Turtle

Gaffney and Meylan 1988

Meiolania: Survivors in ArmorMeiolania platyceps

C. Houck

F. Ippolito.

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 long-term 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

A. Teti

Glyptemys muhlenbergii

Loxodonta africana

The Whale in the TurtleDermochelys coriacea

C. Safina

“Mammalian” Bone Growth

Wyneken et al. 2008

Giant Turtles

R. Somma

Stupendemys geographicus

F. A. Lucas

Archelon ischryos

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. JonesM. Marchand

Nest Site Selection & DiapauseCann 1998

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

Habitat Loss

Unsustainable Use

Disease

Global Turtle Survival Crisis

Invasive species

Global Climate Change Pollution

Primary feeder markets of

turtleimports into

China……have now reached into India, New

Guinea, Africa, and the United

States

IUCN RED LIST CATEGORY STATUS FOR THE WORLDS 265+ TURTLES

23

48

6242

12

74

22

ExtinctExtinct in WildCritically EndangeredEndangeredVulnerableLower RiskData DeficientNot Evaluated

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

58 species of five families in North America

Turtle Priority Areas

The Tortoise and the Hare

Thank you