Knob-scaled lizard facts for kids
Quick facts for kids Knob-scaled lizard |
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Xenosaurus
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| Species: |
grandis
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The knob-scaled lizard, also known by its scientific name Xenosaurus grandis, is a special type of lizard. It's active during the day (which means it's diurnal) and lives on land (terrestrial). You can only find this lizard in Mexico and Guatemala, making it endemic to these countries. It mostly lives in tropical rainforests, hiding in narrow cracks in rocks called crevices. Its main diet is insects.
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What's in a Name? The Knob-Scaled Lizard
The scientific name for this lizard is Xenosaurus grandis. This name comes from ancient Greek words. Xenos means “alien” or “stranger,” and saurus means “lizard.” The word grandis comes from Latin and means “grand” or “great.”
Its common name, “knob-scaled lizard,” describes its unique look. It has bumpy, "knob-like" scales on its back, which makes it easy to recognize.
Lizard Family Tree: Taxonomy
There are five different types, or subspecies, of the knob-scaled lizard. These subspecies live in different parts of the lizard's home range. Scientists are currently studying them to see if some of these subspecies should become their own separate species.
The knob-scaled lizard is listed as a vulnerable species by the IUCN Red List. This means its population is decreasing, and it needs protection.
How the Knob-Scaled Lizard Looks and Lives
Appearance
The knob-scaled lizard has a flat head and body. This flat shape helps it squeeze into tight rock crevices, where it spends almost all its time. This is a great adaptation for staying safe!
Its color can be dark gray or dark brown, often with lighter bands or blotches. It has a forked tongue, similar to a snake's, and small, sharp, fang-like teeth.
Body Size
On average, the knob-scaled lizard measures about 6.8 to 12.9 centimeters (about 2.7 to 5.1 inches) from its snout to the base of its tail. This measurement is called snout-vent length (SVL).
Unlike some other lizard species, male and female knob-scaled lizards are about the same body size. However, males usually have bigger heads, both in length and width, compared to females.
Body Temperature
The knob-scaled lizard is a "thermal conformer." This means its body temperature changes to match the temperature of its surroundings, like the air and the rocks it lives on. Its average body temperature is around 22.7 degrees Celsius (about 72.9 degrees Fahrenheit).
Since these lizards mostly live on the ground and in rock crevices, the temperature of the air and rocks is very important for them. Lizards living in dense tropical forests, where less sunlight reaches the ground, might have different body temperatures.
What Do Knob-Scaled Lizards Eat?
Lizards in the Xenosaurus family, including the knob-scaled lizard, live only in rock crevices. This lifestyle means they are "opportunistic" eaters. They mostly eat whatever insects crawl or fly past or into their rocky homes.
Their diet mainly consists of insects. Sometimes, they might even eat other small lizards! Their favorite meals include:
- Beetles (called coleopterans)
- Flies (called dipterans)
- Grasshoppers, crickets, and locusts (called orthopterans)
- Millipedes and centipedes (called myriapods)
They eat the most flies by number, but grasshoppers and crickets make up the biggest part of their diet by volume.
Behavior
The knob-scaled lizard is active during the day. It's an "ambush predator," meaning it waits quietly in its rocky crevice home. When an insect comes close, it strikes quickly and by surprise!
These lizards are quite solitary and can be aggressive. They often fight with other knob-scaled lizards over their territory.
Reproduction and Life Cycle
Knob-scaled lizards are viviparous. This means they give birth to live young, instead of laying eggs. After about nine months, the mother lizard gives birth. Most litters have three babies, but sometimes they can have two to seven.
Male knob-scaled lizards become adults around 28 months old. Females mature a little later, at about 32 months. It's also possible that these lizards don't have babies every single year.
Where Do Knob-Scaled Lizards Live? Geographic Range
There are five main areas where you can find knob-scaled lizards. These are in Southern Mexico and Guatemala:
- Central Veracruz
- Southern Oaxaca
- North-central Oaxaca
- The highlands of central Chiapas
- Central Guatemala
These separate areas have led to the five different subspecies of X. grandis: X. g. grandis, X. g. agrenon, X. g. arboreus, X. g. rackhami, and X. g. sanmartinesis.
Habitat
All subspecies of the knob-scaled lizard live only in rock crevices. This allows them to live in many different types of environments, including:
- Dry, desert-like areas (xerophytic vegetation)
- Tropical rainforests
- Cloud forests
- Oak forests
- Tropical deciduous rainforests
These lizards are very attached to their homes. They spend about 95% of their entire lives in just one or two rock crevices!
Conservation Status
The knob-scaled lizard is currently listed as a "vulnerable" species by the IUCN. This status is due to several reasons:
- Their populations are broken up into smaller groups.
- The total number of lizards is decreasing.
- Their habitat is shrinking and becoming less healthy.
Their habitat covers only about 20,000 square kilometers (about 7,700 square miles). The biggest threats to these lizards are humans destroying their homes and trapping them for the international pet trade.
Eagles are a natural predator of the knob-scaled lizard, but they don't threaten the species as a whole. However, warmer temperatures in their habitat can cause more lizards to die, which is another potential threat.
Temperature and Survival
Higher temperatures have been linked to higher death rates for knob-scaled lizards. For example, during the wet season of 2003-2004 in Southern Mexico and Guatemala, the average temperature was 24.3 degrees Celsius (about 75.7 degrees Fahrenheit). This was one of the warmest wet seasons in 34 years.
During this warmer period, the death rate for young lizards (yearlings) jumped from 19.23% to 65.51%. For older adult lizards, the death rate increased from 39.56% to 56.76%. If temperatures keep rising, the survival of the species will be even more at risk. Currently, about half of the wet seasons are warm enough to be considered bad for the species.
Population and Growth Rates
As of 2004, the knob-scaled lizard had a survival rate of 70.5% and a growth rate of 0.851. While these numbers might seem low, the knob-scaled lizard is actually doing quite well compared to many other lizard types.
However, the population is currently decreasing. This is mainly thought to be caused by human development destroying their habitat. If habitat destruction stops, scientists believe the population should become stable or even grow.
