ORNATE SPINY TAILED-LIZARDS

By

Ben David Osnat and Molco Danny
(Copyright 1999)

(Editor’s Note.  I have corresponded with Danny for several years. Osnat is a desert tour guide in Israel and Danny is an Eilat Mountain nature reserve ranger. Their research on wild populations of Uromastyx ocellatus ornatus is one of  few field studies dealing with this beautiful lizard. Importantly, it is the only field study I am aware of that followed wild animals for multiple years.  There is much to be learned by reading this information. The authors were concerned that too many conclusions may be drawn from captive populations and then extrapolated to wild populations (e.g., age of sexual maturity).  This is a valid concern and as herpetoculturist we must always keep in mind the captivity is ecologically very different than the “wild.”  I have made some minor editorial changes to make the translation more understandable to an English speaking audience.    Randall L. Gray   (temporarily retired Uromastyx breeder!  9/26/99)

The following data is based on 4 years of field research on Uromastyx ornatus with care to the wild population and just "open your mind about it".

So far we have more then 700 hours of field watching.

Growth Rate

In nature the growing rate is very slow comparing to growing in captivity.
Weight in grams, length in millimeter snout to tip's tail.
Hatchling the same size: 5 gr. and 85 - 95 mm, long.
At one year they are 22 - 32 gr. and 150 - 175 mm, long.
Second year of age they are around 50 gr. and 213 mm, long.
Third year they are between 98 - 116 gr. and 247 - 266 mm, long.
Fourth year they are more then 180-gr. and more then 275 mm.
We think that around this size they become sexually mature, in age of four years. A big difference according to the high speed growing in captivity.  (  Editor’s Note: The following is a quote from Audrey Vanderlinden’s article which is posted on the Uromastyx Home Page)  “My observations indicate that sexual maturity can occur as early as 11 months in captivity without any winter brumation". We think this is great but can cause health problem. (referring to 11 month old ornates reproducing).

Incubation

"Incubator at 90F for approximately 72 days". It is too long!
So far we found three incubation burrows. We dug the first one:
there was 11 empty egg and the temp' was 35 CC = 96 F humidity around 32 degree and last 64 days. The other two belong to the same female the incubation took 56 days, that mean even higher temp'. this year she have 13 hatchling and they all speared out in 4 days
We think 96 - 98 F can be the best.

It very important to put a parent's dry drops (fecal)  in the hatchling cage for the first few days.

THE FOLLOWING ARE SOME QUESTIONS THAT TROY JONES ASKED DANNY.  RANDY GRAY
EDITED THE RESPONSES.

QUESTION: Danny did you notice any winter hibernation of the ornate Uromastyx
you are studying?

DANNY'S REPLY: It does not seem there is any hibernation.  Although there is
not much activity from December to January I can find some of  them basking
on sunny days  when the temperature is above 69 F.  I have also observed them
feeding when the temperature is 72 F in the shade.

QUESTION: Danny how did you measure the incubation temperatures?
Over what period of time were these measurements taken?

DANNY'S REPLY: We dug up the burrow and measured the temperature which was
35.2 C (96F). Then we put a probe from a min/max thermometer  into the burrow
where we found the egg and covered the burrow again. The following summer we
took a few measurements during incubation which were a constant 35.2 cc (96F).

While digging her burrow, the ornate Uromastyx would enter head first and
then exit tail first. The day that she came out head first we knew she had
laid the egg. In addition, that evening she blocked the burrow. This
information allowed us to determine the total incubation time.

QUESTION: During your field studies have you observed the U.ornates in the wild
eating insects?

DANNY'S REPLY: They don't eat insects. But the answer is actually more complicated.
We have more then 50 hours of feeding observations and found  they eat mostly flowers
and fruits. An analysis of  their droppings showed that insects make up only 1% of  the diet.
Some of  these insects were probably on the fruits and flowers they consumed.  We did
a stomach analysis of a dead lizard and found it full of  Acacia flowers and a few little ants.

QUESTION: Do the young eat more insects than the adults?

DANNY'S REPLY: So far it does not appear that they do. See above answer.

QUESTION: Do the Wild U.ornates eat more insects during a specific season?

DANNY'S REPLY: So far it does not appear that they do. See above answer.

A couple pictures taken by Danny Molco, of the U.ornates in  the wild.
Picture #1 Click here
Picture #2. Click here.
Picture #3  Click here
Picture #3 Uro ornatus eating Acacia flower photo by Yakob Eazer.
Picture #4 Click here
Picture #4 Uro determination photo by Danny Molco.
Picture #5 Click here
Picture #5  Uro ornatus mating by Osnat Ben-David.
Picture #6 Click Here
Picture #6 Another picture of Uro ornatus mating by Osnat Ben-David.
Picture #7 Click here
Picture #7 Uro ornatus fighting by Danny Molco.
Picture #8 Click here
Picture #8 Another Uro ornatus fighting by Danny Molco.