Reproductive Biology of the Crocodylia

173 Pages·2021·3.929 MB·English

by  Valentine Lance

Reproductive Biology
of the Crocodylia
This pageintentionallyleftblank
Reproductive Biology of
the Crocodylia
Valentine Lance
Vice Chairman for Science for the Crocodile Specialist Group of SSC/IUCN and
Advisor to the Crocodilian Advisory Group (TAG) of the AAZPA,
California, United States
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Contents
ACKNOWLEDGMENTS................................................................................vii
INTRODUCTION...........................................................................................xi
CHAPTER 1 Phylogeny and fossil history....................................................1
CHAPTER 2 History and growth of knowledge............................................7
Earlyanatomicalstudies....................................................................20
CHAPTER 3 Life history and ecology.........................................................33
Multiplepaternity................................................................................35
Nest-sitefidelity..................................................................................36
Someuniqueandunusualfeaturesofcrocodyliansorsome
crocodilianoddities.............................................................................36
CHAPTER 4 Growth, sexual maturity, and senescence............................55
Senescence.........................................................................................62
Sexualmaturity...................................................................................63
CHAPTER 5 Anatomyof the male reproductive tract...............................65
CHAPTER 6 Male reproductive cycle.........................................................71
CHAPTER 7 Anatomyof the female reproductive tract............................77
Theovary.............................................................................................78
Theoviducts........................................................................................79
Spermstorage....................................................................................81
v
vi Contents
CHAPTER8 Female reproductive cycle.....................................................83
Courtshipbehavior.............................................................................84
Vitellogenesis......................................................................................85
Nesting................................................................................................87
Eggs.....................................................................................................90
Clutchsize...........................................................................................91
CHAPTER9 Sex determination, embryos, and teratology........................97
CHAPTER10 Captive breeding,farming, and ranching.........................103
Doubleclutches................................................................................112
CHAPTER11 Environmental contamination............................................113
Heavymetals.....................................................................................115
CHAPTER12 Conservation.......................................................................117
REFERENCES...........................................................................................121
INDEX......................................................................................................155
Acknowledgments
A large number of colleagues have helped me at many different times, in
many different ways, and in many different locations, to collect the informa-
tion included in this book. Crocodile researchers are, in my experience, the
friendliest group of people I have ever had the pleasure to work with, and
who are more than happy to share any information (maybe everyone else
thinkstheyarealittlestrangeandsoarehappytofindsomeonewhowilllis-
ten to them). First, late Prof. Roland Coulson, for his friendship, unstinting
help, and advice, and for the example of his clear and elegant prose: anyone
witheven theslightestinterestin alligatorbiologywhowas fortunate enough
tovisit withtheProfinhislaboratoryinNewOrleanswasgivenawarmwel-
come and invited to share whatever meal he was cooking at the time (often
red beans and rice), and to listen to his yarns—a wonderful story-teller, an
unrepentant anglophile, and a true gentleman in every sense of the word. He
knew London (the city of my birth, better than I did), where he lived during
World War II and completed PhD in biochemistry from the University of
London while in the British military (for a brief biography, see Dessauer,
1989); Ted Joanen, apioneer in field research on alligators, alligator farming,
and alligator biology, and the individual who first introduced the then-
controversial concept of the harvesting of wild alligators as a renewable
resource. HissupportandhelpwhenIfirst venturedintothis areaofresearch
were critical. Without the long hours, he volunteered to help catch alligators
when he could have been home in bed, the work described in the pages that
follow would not have been possible; Dr. Ruth Elsey, formerly my student
and now one of the world’s experts on alligator management and biology, a
long-term collaborator on some pioneering experiments, an exacting editor,
and a good and true friend; Dr. Kent Vliet, a friend for more than 40 years
(hasitreallybeenthatlong),acrocodilophileextraordinaire.Kent’sunrelent-
ing pursuit of every last possible piece of information on crocodilians has
resulted in a superb collection of more than 10,000 articles that have some
mention of caimans, alligators, crocodiles, and fossil crocodilians. In addi-
tion, I would like to thank Dr. Brandon Moore for access to his published
and unpublished materials on the detailed functional anatomy of the
vii
viii Acknowledgments
crocodilian intromittent organ, or phallus. A number of his photographs are
included in this book.
I would also like to thank Jeff Lang, a friend for many years, for keeping me
honest—a rigorous and exacting scientist, a superb field biologist, a world
authorityoncrocodiles,andespeciallythegharial(Gavialisgangeticus),acroc-
odilian he has studied in India for many years, and a crocodile that he dis-
covered does not behave as other crocodiles. My visit with him on the
Chambal River (a tributary of the river Ganges) in Uttar Pradesh, India,
where he has established a research post in an isolated village that seems lit-
tle changed from some hundreds of years ago, is an experience Itreasure.
In the years of working with alligators I have been fortunate to meet with,
and establish lasting friendships, with an extraordinary group of people,
namely, the Crocodile Specialist Group, or CSG, of the IUCN (International
Union for the Conservation of Nature). The CSG is a group of volunteers
with a passion for crocodiles that meets every 2 years, usually in a country
with healthy crocodilian populations, to discuss the latest information on
the management of wild populations, farming, research, veterinary science,
and trade in crocodile products (their parties are famous). A simple e-mail
will get an instant response to any odd question on crocodilians. Among
those whom Ipesterwithfrequent questionsisDr.ChrisBrochu, paleontolo-
gist andworld experton crocodilesinthefossil record.Hemust live attached
to his computer, for it seems that any time day or night I send a question, I
get an instant response. Charlie Manolis, who has worked with the notorious
man-eater (Crocodylus porosus) and the Freshwater Australian crocodile
(Crocodylus johnstoni) of northern Australia for more than 30 years and is a
great source of information, always freely given. Grahame Webb, chairman
of the CSG, who, despite his almost incomprehensible Australian accent, has
advocated stronglyanddiplomatically(and successfully)on the international
stage for the conservation and sustainable use of crocodiles. In addition, my
colleagues of “Proyecto Yacare,” Carlos Piña, Alba and Alejandro Larriera,
Pablo Siroski, and Melina Simonici, in Sante Fe, Argentina, have taken me
along on their field research with the “gauchos” and have welcomed me into
their homes. My Brazilian colleagues, especially Luciano Verdade and the
indefatigable Zilca Campos—both of whom have taken care of me during
my many trips to Brazil. An additional and heartfelt thanks is due to Zilca
for nursing me through a bout of pneumonia I contracted in the tropics of
Brazil (I think it was due to the extreme air-conditioning at a crocodile meet-
ing in Manaus I attended shortly after I got off the plane from the United
States).
Acknowledgments ix
A large number of students and volunteers helped both in the laboratory
and the field, among whom, Lori Jackintell, Willow Gabriel, and Lisa Morici
completed master’sdegrees on alligators.
I would also like to thank Dr. Victoria Mattey for a superb translation from
the Russian of the paper by Sovienski (1889), and my daughter Kio for her
help in making my translations from papers published in Spanish a little
more accurate. Also, thanks to Drs. Sterling Nesbitt and Michele Stocker, pro-
fessional paleontologists, for their advice on crocodiles in the fossil record
andon the evolution ofthe Crocodylia.