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A Secure Habitat - Darrell Senneke
Copyright © 2003 World Chelonian Trust. All rights reserved
When building an outdoor habitat for tortoises and turtles people are generally very concerned with providing a healthy and attractive environment. One thing often overlooked is security. A secure habitat must provide for two things. This is to be both escape proof and invasion proof. Luckily the same precautions can provide for both of the above. At the end of this article I will discuss the design for what can be considered a "secure" pen. At this point though I will detail some of the dangers. I will attempt to make this as all encompassing as possible. Often various publications caution against only what is a problem in the author's geographic area, for the novice this can be misleading.
The dangers of escape tend to be species specific. While a T. horsfieldii can dig under any wall a G. pardalis is more likely to either push under it or actually climb over it. I myself have seen a Clemmys insculpta climb over a 1.2-meter chain link fence. Research your species carefully and take precautions based on its particular habits.
Each type of predator presents its own unique problems, I will cover as many as I can here but I would advise talking to area keepers and gardeners to find out the pests in your area. Be aware that what may not be a problem to the keeper down the street may be a problem for you based upon your species or the size of your animals.
Hedgehogs: Hedgehogs can dig under a wall or climb over it. They are nocturnal and so are usually only a danger at night. They are a danger to turtles and tortoises because they will chew on any part of the animal they can get to.
Ravens: Ravens will pick up and carry off young and juvenile tortoises and turtles. They are not considered a threat to large animals though anything the size of an adult T. horsfieldii and under is at risk in an area with a population of ravens.
Crows and Seagulls: Crows and seagulls offer the same problems as ravens though their smaller size makes them less of a threat to juveniles.
Raptors: Hawks and owls can and will eat any young chelonia they can get to. Because owls hunt by night they are less of a threat than hawks but must not be disregarded if one is keeping crepuscular species.
Herons: Herons are masters at plucking hatchling turtles out of ponds.
Skunks: Skunks can dig under a wall, go over it, or if given enough time and based on materials chew through it. They pose the same threat as hedgehogs with the additional danger of robbing any nests present.
Raccoons: In the United States and Canada raccoons are among the most feared of chelonian predators. They can climb or dig under any fence or wall. In addition to this they possess hands and are large giving them the needed dexterity and leverage necessary to remove covers from pens or unlatch the doors of hutches. They are masters at finding any nest that is not protected. They can easily pick up and carry off an adult T. ibera resulting in the loss of the animal even if they do not kill it. They are excellent swimmers and can easily capture aquatic turtles. They hunt from dusk to dawn. The photo at right is the result of an assumed raccoon attack on a Wood Turtle (Glyptemys insculpta) in the wild.
Opossum: Opossum are excellent climbers and can severely damage the heads and legs of chelonia.
Weasels: Weasels, mink and ferrets are adept at squeezing through incredibly small openings and pose a significant danger in areas where they are found.
Canines: Dogs should never be allowed unsupervised access to turtles or tortoises. Dog bites are among the most common of all tortoise injuries. Coyotes pose the same danger as well and hunt at night.
Felines: Feral housecats pose a threat to hatchlings, bobcats pose a threat to all tortoises and turtles.
Fireants: Fireants kill hatchling tortoises and destroy eggs as well. Fireants must not be allowed in the enclosure.
Ground Wasps: Yellow Jackets and other ground wasps will sting any turtle that ventures too close to their nest. Unfortunately in any but the largest pens a turtle or tortoise can not avoid doing so. Wasp nests must be removed.
Mice: Mice are generally not a problem unless the tortoise is hibernating. Sustained chewing by mice on hibernating tortoises is a very real danger.
Rats: Rats are expert at finding access into pens where they prey on hatchlings and juveniles.
Humans: There is no absolute protection against a dedicated human predator. The best that can be hoped for is to protect against the opportunistic ones.
Precautions may take three forms, subsurface barriers, surface barriers and deterrents.
Subsurface Barriers: A barrier should be placed below ground level to prohibit your animals from digging out and to bar predators from digging into your habitat. There are various forms that this barrier can take.
Often for non-burrowing tortoises and turtles bricks, tiles or concrete blocks are placed horizontally beneath the perimeter walls. Generally predators dig once they meet an obstruction. The presence of the bricks removes the point of possible access away from the wall thus reducing the chances of burrowing in. Please note! This precaution is not sufficient to keep T. horsfieldii and G. sulcata from burrowing out. If using this method a few centimeters of soil or mulch should be placed over the tiles or bricks inside the perimeter wall to cushion the fall of any turtle or tortoise attempting to scale the wall, thus preventing cracked and chipped carapaces.
Another method is to build the external walls upon a foundation of concrete poured into a trench ringing the perimeter of the habitat, this is effective but also considerably costly.
A third option is to dig a trench a minimum of 30 cm deep just inside or outside the perimeter of the wall. In this trench is buried hardware cloth or poultry netting which is securely attached to the walls. The bottom of this netting is bent in to prevent digging out or out to prevent digging in based on concerns. The digging animal meets the wire barrier both in front and below their excavation and is thwarted in their attempt to gain passage. If one is keeping an accomplished burrowing animal such as the aforementioned T. horsfieldii and G. sulcata the depth of this trench should be considerably deeper, a minimum of 60 cm.
If attempting to retrofit an existing pen a subsurface barrier can be installed in one day (depending on soil conditions) by pounding aluminum or steel sheeting into the earth around the inside perimeter of the pen.
If installing subsurface solid barriers in compacted or clay based soil it is a good idea to also incorporate drainage into the design of the pen. A simple PVC pipe filled with coarse gravel looping under the barrier will be sufficient to remove surface water.
The height of the perimeter walls will be determined by the size of your charges, I generally use as a rule of thumb walls that are a minimum of one and a half times the length of the tortoises or turtles in the habitat. For example, a thirty-centimeter G. pardalis would require a wall a minimum of forty-five centimeters high. Further security can be provided by doing any of the following based upon your needs. Be aware that turtles and tortoises tend to pile up on one another in corners thus providing an unanticipated means of escape.
To simply guard against escape a simple ten-centimeter overhang on the top of the perimeter walls can be sufficient to protect against your charge scaling them. As a means of adding some extra insurance bench tops can be built onto the corners of the pen offering more overhang as well as supplying a place to sit for the keeper and a shady place to hide for the chelonian.
For protection from avians plastic bird netting such as that used in orchards or gardens can be suspended in a canopy-like application that keepers can walk under. Bird netting can also be stapled onto frames that are put on the top of the pens to discourage winged predators. These frames can be built hinged or removable for esthetic purposes.
For increased protection wire poultry netting or hardware cloth can be attached to frames that are fitted to the top of the pen. Please note! These frames should be strong enough to support a 20-kilogram animal. These can be hinged for ease of removal. It may be wise to find a means of securely fastening these frames to the top of the pens. Rubber tie-down straps (sometimes called cargo or bungee cords) can be attached at all four corners and stretched to hook into eyebolts screwed into the walls of the habitat. In extreme cases latches and padlocks can secure tops.
A second layer of protection can be provided by perimeter fencing the entire tortoise area. Anti-burrowing precautions can be taken on the perimeter fence to effectively turn the entire yard or garden into a large enclosure.
Deterrents would be classified as precautions taken to keep a predator away from the enclosures providing another layer of protection.
Electric Fencing: In areas with a burgeoning raccoon population many keepers have turned to electric fencing as a deterrent. The purpose of the electric fence is to prevent undesired animals from entering an area. High voltage electrical impulses are applied to a "live" fence wire by an energizer. This impulse lasts only thousandths of a second but is repeated every second or so. An animal that strays into contact with the live wire completes a circuit between the live wire and the soil or earth wire (if one is installed). The result is an electric shock sufficiently unpleasant to cause the animal to move rapidly away from the fence before the next electrical impulse. Animals soon learn not to touch the live wire or approach the fence too closely. Gate clips may installed to allow the keeper access to the area being protected without fear of shock.
There are now solar powered electric fence energizers on the market allowing one to use this protection in areas away from a source of electricity. They require a minimal amount of daylight to recharge and are quite effective.
Predator Urine: Another deterrent is predator urine. This method is based upon the principal of duplicating the use of urine by animals in the wild. Predators mark the perimeter of their territory with urine as a warning to competitors and a welcome to potential mates. Potential prey animals avoid such marked territories. Coyote urine has been shown to be effective against skunks and raccoons. The perimeter of the turtle or tortoise area is "marked" with the purchased urine by the keeper.
Ultrasonic Motion Sensing Animal Repellers: There are a number of versions of this deterrent on the market available in gardening catalogs. The principle by which they work is as follows. The built-in motion sensor or passive infrared sensor (or a combination of both) detects an animal entering the area and emits a piercing, high decibel alarm. It startles the animal and frightens it away. Since it is ultrasonic you and your neighbors cannot hear it and you can easily adjust the sound from ultrasonic to a more aggressive audible pitch for persistent predators. While this may be effective I question the effect of its activation on the inhabitant of the enclosure.
Water Spraying Deterrents: Taking the above method a step further is the water spraying deterrents. This piece of equipment is able to sense an animal by recognizing both its movement and body heat. After activation, this remarkably effective deterrent releases a harmless three second burst of water through a pulsating sprinkler head with the accompanying noise associated with water being turned on. This causes unwanted intruders to depart the area. Its peak operating conditions are at night when unwanted animal presence is at a maximum. There are two versions of this on the market that I have found. Water De-Fence and Scarecrow, both seem to meet the same specifications. They consist of a hose attachment at the bottom, attached to a sixty-centimeter aluminum pipe on which sits a battery operated motion/heat detector and a pulsating sprinkler head. When motion or heat is detected a valve is opened which allows the blast of water to flow to the sprinkler. The mechanism automatically resets after each use. This is available from finer gardening catalogs and is effective against most predators. As an added bonus this may also have effectiveness against door-to-door solicitors.
Diatomaceous Earth: When put in a fifteen-centimeter band around the pen Diatomaceous Earth is an effective Fire Ant deterrent. Millions of years ago the seas abounded with single-cell plants called Diatoms. The fossilized remains of these Diatoms were transformed into a chalky material called Diatomaceous Earth. The inherently abrasive nature and high absorbency of Diatomaceous Earth give it a unique mechanical killing power over insects. The ultra-fine slivers of Diatomaceous Earth attack an insect's waxy exoskeleton and through abrasion and desiccation, provided an opening for the natural dehydrating effects of Diatomaceous Earth to absorb the insect's body fluids. Death by dehydration follows. This material was once used frequently as a flea powder for dogs and cats but has been recently advised against by some veterinarians because of inhalation and cornea abrasion risks during its application. Because of this I would only advise its use outside the pen. This material needs to be reapplied after rains.
When constructing an outdoor enclosure incorporating barriers and deterrents as precautions against escape and invasion is strongly advised. This will do much to ensure that your particular species and the predators endemic in your geographic area do not come into contact with each other. Following these suggestions your charges not only will have a habitat that is conducive to their dietary and environmental needs but one that is secure as well.
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