Tyrannosaurus Pets

Savannah Monitor (Bosc - Varanus exanthematicus) Care Sheet


Savannah or Bosc’s monitors are the most commonly encountered monitors in the pet trade.  If properly cared for and housed correctly they can make a good pet.  Being a large predominately insectivorous lizard makes the Bosc expensive to both house and feed.   A baby monitor should be kept in a vivarium 1.2m x 60cm x 60cm.  Any smaller and it will last no time as they grow quickly, any larger and it will be hard to tame them and even harder to catch them.  This size tank should last for around a year.  The animal will then need moving into the adult enclosure.  This needs to be at least 1.8m x 90cm x 90cm, preferably 2.4m x 1.2m x 1.2m.  The white throat monitor is a close relative to the Bosc, and its care may be considered identical.


Housing your Bosc Monitor


Bosc monitors are diurnal (day time active) lizards found throughout central Africa.  They will normally seek out a safe place to spend the night about ninety minutes before the sun sets.  If you get back from work at 6pm there is no point having the lights going out at 7pm as the lizard will be asleep by the time you get in.  If the lights are on a time switch set for 9am to 11pm then when you get in at 6pm the lizard will still be active and looking for food.  Setting the lamps on a timer helps keep the lizard in a comfortable routine.  It is best to keep them on a day length of between 12 – 14 hours


Lighting the vivarium


In a smaller vivarium for a baby lizard a strip light (desert rated 12%UVB are the best) is used to provide the UVB.  The UV output is only effective for a limited range, the animal must be able to get within 30cm of the tube in order to utilise the benefits of the UV.  The optimum position for the UV is directly above the animal.  With the limited range of the UV it is advisable to use a reflector.  This nearly doubles the available output of the tube, and increases the range to around 45cm.  UV tubes have a short effective lifespan.  They will still be producing light after a year, but the UV output will have dropped to zero.  UV tubes must be replaced every four to twelve months depending on brand and output.  Due to the size of enclosure involved several tubes may be required to produce enough UV to cover the tank.  The new T5 lighting systems are better than the older T8 units.  A UV tube will struggle to provide sufficient UV in an adult enclosure.   In these larger tanks the best option is a mercury vapour flood lamp (such as Zoomed’s PowerSun UV), these give out a concentrated amount of UV over the basking area.  Using this lamp in combination with a T5 strip light gives a better light output over the whole tank.


Heating the vivarium


Savannah monitors can tolerate night time temperatures as low as 15’c, but they are more comfortable being kept between 20’c – 24’c.  Using a ceramic heater on a night drop thermostat will provide a gentle back ground heat.  In an enclosure for a young animal a single ceramic heater plugged into a thermostat will provide plenty of heat.  In a larger adult enclosure several heaters will be required to provide a large enough basking area for the lizard to reach its optimum temperature at a natural speed.  The sensor for the thermostat should be about a third of the way in from the cool end of the tank.  It should come in at the top of the tank and hang down 2” – 3” above the substrate.  To make the tank look neater secure the sensor cable with conduit, but make sure that the black portion of the wire is exposed to the air in the tank.  Set the thermostat to 26’c.  This estimate should get the tank close to the desired temperatures.  The thermostat will heat the point in the tank where the sensor is to 26’c, the temperature at the cool end should be a couple of degrees cooler than this (around 22’c – 24’c), while at the opposite end of the tank at the basking area the temperatures should be around 40 – 42’c.  If you are having trouble getting the basking temperature high enough, place an elevated platform under the lamp. 


Raising the height of the basking area will increase the basking temperature.  A pile of logs or rocks make a very good basking platform, however as these lizards are very powerful animals ensure that any heavy decoration is securely fastened in place to prevent the monitor from dislodging it, breaking the glass of the tank, or becoming trapped underneath it.  When checking the temperatures in the tank always place the thermometer where the animals are going to be.  The most important temperatures are the basking point, and the cool end.  Check the temperatures in the tank after two hours.  If they are correct leave a further two hours to check they are stable.  If the temperatures are not quite right tweak the thermostat and leave for a further two hours and then recheck them.  Do not adjust the thermostat too much as a small tweak can make a large difference to the tank temperature. Always leave at least two hours between adjusting the thermostat and checking the temperatures to allow everything to settle down.


The basking area needs to be at least as big as the lizard that will use it.  A single high power lamp used to heat a large cage can actually over heat or even burn the lizard as the high temperature is too concentrated.  A better method is to use two or three lower power lamps to create a larger hot spot.  If you have a warm house and so no night time heat is needed then use two basking lamps connected to a dimming thermostat and a mercury vapour UVB lamp. Mount these in a triangle with each lamp about 30 - 40cm away from the other two.  This will create a nice big hotspot for your lizard.  If you need to heat the tank at night use two ceramic heaters on a thermostat together with the mercury vapour lamp.  If you use a thermostat with a night drop facility then the tank will automatically run at a lower temperature overnight.


Feeding Your Savannah Monitor


Savannah monitors are predominately insectivorous.  In the wild their juvenile diet is almost entirely composed of invertebrate prey (crickets, slugs, millipedes, and beetles).  As they get older the lizard’s diet expands to include hard shelled prey items like giant land snails.  The monitors are opportunistic feeders and will eat anything they can over power.  However vertebrate prey (such as rodents), still make up less than 1% of their diet.


In captivity savannah monitors are highly prone to obesity.  The main factor for this is the animal’s food.  They should be fed as close to their natural diet as possible, a wide variety of live insect prey such as crickets, locusts, mealworms, cockroaches, slugs, snails, and earthworms should be offered.  Any high fat, high protein food such as rodents should be offered only occasionally, once every three weeks or so.  Failure to provide the correct diet will quickly result in an overweight monitor.  Bosc monitors can also become lazy, feeding only large prey items means they have to work less for the food.  This inactivity can also result in an unhealthy over weight animal.  It is better for the lizard to be offered a large number of small prey items that take it a long time to catch.  Do not allow the lizard to dictate what it wants to eat, a hungry lizard will catch what you offer it, a lazy over fed one will only go for its favourite food items.


While young the monitor should be offered food daily.  It can be worth feeding several small meals to keep the animals activity levels up.  As the lizard gets older it will no longer require feeding every day.  An adult Bosc can be fed three or four times per week.  Because the lizard requires access to a high basking temperature to digest its food properly, they should not be fed within four hours of the lights being turned off.  It is worth working out when you want to feed your pet when setting the time switch for the lamps.


It is also important to look after the live food you are feeding to your lizard, as “you are what you eat”.  The better quality food you can offer the healthier your monitor will be.  Keeping crickets in a well-ventilated container such as a cricket keeper will increase their health and lifespan.  A range of propriety insect foods are available these are normally fortified with calcium.  These are an excellent way to gut load the food. 


A full spectrum vitamin and mineral supplement (such as Nutrobal or Repton) should be added to the food twice per week, and a pure calcium supplement should be added a further three times per week.


As the monitor grows and starts to eat bugs less frequently adjust the number of supplemented feeds so that the ratio remains the same.  An adult lizard should be getting the full spectrum supplement once per week, and the pure calcium once or twice per week.


To dust the crickets place 8 – 10 appropriate sized insects in a large jug or clear plastic bag.  Add a pinch of powder and shake to coat the insects.  Feed these to the monitor.  If these are all eaten and the lizard is still hunting, feed another 2 – 3 insects; keep adding more bugs until the animal is full.  This extra food does not need to be dusted.


Daily care of your monitor


Monitors should be offered fresh water every morning.  Some monitors enjoy soaking in their dish, and can like to defecate in the water bowl.  If your monitor does this it will make cleaning the tank a lot easier.


When you change the water examine the tank for any mess, and remove it.  If the spot cleaning is done regularly then the tank will only require a full cleanout once every four to six weeks.  Bosc monitors like to dig.  A deep substrate helps to keep them active digging for food, and building tunnels to sleep in.  Most keepers have a lot of success using a 50/50 mixture of heat treated top soil, and play pit sand as a floor covering.  Ideally this should be at least twelve inches deep.


When doing a full clean out put the monitor somewhere safe.  Remove and clean all decoration and dishes from the tank.  Remove all the old substrate and clean the tank.  When the tank is dry, put in clean substrate, and replace the décor.  The lizard can then return home.


When cleaning the tank do not use household detergents and disinfectants as these can be toxic to reptiles.  There are a range of reptile specific cleaners available.

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Tyrannosaurus Pets