Red-footed tortoise

Appearance

Red-footed tortoises show gender, regional and individual variations in color, shell shape, and minor anatomic characteristics. Adult red-footed tortoise carapaces are generally an elongated oval with sides that are nearly parallel, although the sides of males may curve inwards. They are fairly highly domed and smooth with a rather flat back. There is often a high point over the hips and a small sloped section over the neck. The vertebral and costal scutes are black or dark brown with a pale yellow areole in the center. The marginals 'tuck under' along the sides and flare slightly over the limbs. They are dark with the pale aureole along the middle of the lower edge. The nuchal scute is absent, and the marginals over the tail are joined as one large supracaudal. Growth rings are clearly evident in most individuals but become worn smooth with age.

The plastron is large and thick along the edges. The gulars do not protrude much past the front of the carapace. The plastron of a male is deeply indented, and the anal scutes may be used to sex the animal while the color pattern varies by region.

The head is relatively small with a squared-off profile and flat on top, longer than it is wide. The eye is large with a black iris, and rarely any sclera visible around it. The upper jaw is slightly hooked, and the upper jaw is notched in the front middle. There are fifteen to twenty 'teeth' or fine grooves on each side of each jaw. A nearly circular tympanum is located behind and below the eye and is covered with a dark scale. The scales of the head are generally smallish and irregular, becoming small and pebbly on the neck. Many of the scales are colored pale yellow to brick red, especially those on the top of the head, above the tympanum, around the nostrils, on the lower jaw, and on the sides of the neck. Males are usually slightly more colorful than females, and colors vary by region.

The limbs are generally cylindrical with four claws on the forelimbs and five on the hind, but no visible toes. The forelimbs are slightly flattened and the front surface is covered with large scales, mostly with the same color as the head. They are not as large or protrusive as they are in more primitive species such as the African spurred tortoise. The tail is muscular, varies in length and overall shape by gender, and lacks any sort of claw on the tip.

Average adult sizes vary by region and gender, and 'giants' are often encountered. Red-footed tortoises average 30–35 cm with males slightly larger overall. Red-foots of up to 45 cm are fairly common and over 50 cm are occasionally discovered. The largest known specimen was from Paraguay, was 60 cm long, and weighed over 28 kg. It is unknown if the 'giants' represent diet availability, genetic issues, longevity, or other possibilities.

Hatchling and young red-footed tortoises have much rounder and flatter carapaces that start off as mostly pale yellow to brown. New growth adds dark rings around the pale center to each scute. The marginals of very young red-footed tortoise are serrated, especially over the hind limbs. This probably aids in both camouflage against the leaf litter and in making the small animals harder to eat. Young tortoises are generally more colorful overall.

Distribution

Red-footed tortoises range from southeastern Panama to Venezuela, Guyana, Suriname, and Guiana in the north; down the Andes to the west in Colombia, Ecuador, Peru, and Bolivia; east to Brazil, and along the southern range in Bolivia, Paraguay, and possibly northern Argentina.

Behavior

The red-footed tortoise's climate in the northern part of the range changes little day to day and rarely gets too hot for them, so the tortoises do not need to practice any form of dormancy and can often forage all day long. The tortoises in Moskovitz's study area were most active after 3:00pm while many species from warmer climes would be most active in the morning and evening. Tortoises from the southern parts of the range experience much hotter, colder, and drier conditions than most of the range and aestivate when food becomes scarce. They may eaestivate or brumate when the temperatures are low enough.

Most species of tortoise spend much of their day inactive, and red-footed tortoises generally spend over 50% of the daylight hours at rest. They may rest for even longer after a large meal, with five to ten day stretches being common. One large specimen seems to have stayed in the same position for over a month. Resting tortoises barely move, allowing leaf litter to accumulate on them, and termites have built tunnels on the carapaces of resting red-footed tortoises.

They seek shelter in places that offer thermoregulation and protection from predators. Treefalls are a favored site, as are debris piles, burrows and agouti ), hollow logs, holes, and heavy vegetation cover. They generally try to find tight-fitting resting places, and will occasionally 'wedge' themselves between roots and trunks but remain otherwise exposed. Burrows and holes are often flooded and the tortoises will rest in the water and mud with just their nostrils and eyes exposed. In warmer weather, they press up against moister, cooler surfaces in shelter areas. The tortoises show personal preferences with many individuals always seeking out a specific type of shelter.

Shelters are often communal with as many tortoises as can fit in the space. Good shelters are so important, and visibility is so poor that the tortoises will leave scent trails that they or others can follow. Some shelters are so heavily used by tortoises that there are clear trails in the dirt leading to them, even though individual tortoises may not return to a given shelter regularly.

Besides communal shelters and scent marking, red-footed tortoises also show other signs of semi-social behavior such as lack of aggression at feeding sites, not protecting territory, and group feeding at fruit falls and carrion. Red-footed tortoises often follow each other, usually a smaller one following a larger and quite often males following males but all combinations are seen. Red-footed tortoises have also been observed following apparent scent trails laid by an individual a day or two earlier.All turtles and tortoises start as eggs. Red-footed tortoise eggs are roughly spherical and average around 5.0 by 4.2 cm and weigh 50 g with two to seven eggs in a clutch, although the same female may lay multiple clutches near each other. The incubation period is 105–202 days with 150 being typical.

Reproduction

Hatchlings use an egg-tooth to open the egg. They will stay in the egg or nest for several days. Hatchling shells are bent almost in half in the egg and will take some time to straighten out. The 3.6 by 6.3 cm hatchling's carapace will be flat, somewhat creased from being folded in the egg, and have serrationed sides. Little is known of the daily activities or diet of hatchling wild tortoises. Sub-adult tortoises grow quickly to reach breeding sizes- roughly 20 to 25 cm, depending on the average adult size of the regional variant.

The peak time for courtship and reproduction is the early wet season in April and May although it can happen at any time. Courtship noises and possibly scent cues seem to attract other tortoises to 'courting sites' under fruiting trees such as Genipa When two tortoises meet about a meter apart, they will engage in some specific behaviors to identify the other. The first trigger is head and limb color- the bright red, orange, yellow, or white colors on the dark skin identifies the other animal as the proper species. Next, the larger tortoise will make jerky side to side head movements for two to four seconds. If both tortoises are males, one will either withdraw and retreat, or they may try to ram each other, trying to get their gular scutes under the other one, then pushing them several meters away as quickly as possible. The defeated tortoise is sometimes flipped onto his back in the process. The defeated tortoise will leave the area afterwards. Neither head bobbing nor ritual combat have been observed in tortoises south of the Amazon Basin, possibly due to the lack of yellow-footed tortoises in the area. Males mounting other males, and even females mounting either sex have been witnessed and are thought to show dominance.

If the other tortoise is a female, she will move away and the male will follow, touching her carapace and occasionally sniffing at her cloaca. If the female stops, the male may either wait for her to resume moving or leave. Males make loud 'clucking' sounds during the chase. After trailing, the male mounts the female, his feet planted on the costals of her carapace, rams his anal scutes against her supracaudal, and makes a loud raspy 'bark'. If the female resumes walking, he may fall off and resume trailing. Females sometimes seem to intentionally use low limbs to knock males off. A receptive female will extend her hind legs and lift her plastron as the male plants himself on his own extended hind legs as he works to align their cloacas for insertion. The tail, scutes, and of the tortoise are designed to work around the awkwardness of the shell. The male often leans his head over her head and holds his jaws wide open making calls that get louder. He may bite her as well, sometimes quite aggressively. The shells can make loud clacking noises during the forceful thrusts. The female walks away after copulation, sometimes knocking the male off her.

The female will begin nesting five to six weeks after mating. Digging the nests is often difficult in hard soil. The female may urinate to soften the soil before using her hind legs to dig a chamber about 10 by 20 cm in about three and a half hours. Inexperienced females often dig several partial nests, and even experienced females may abandon a nest they are working on and start another. When the nest is ready, she will lower her tail as deep into the nest as she can and deposit an egg every 30 to 120 seconds. She will recover the nest and tamp the soil down. Females get better at digging, covering, and camouflaging nests over time. After it is covered and hidden, she will often get a long drink of water then find a shelter and rest. Very rarely a red-footed tortoise will lay eggs on the surface, or within a patch of cacti.

As with other tortoises, red-footed tortoises can reproduce most of their lives, although the number of eggs laid and the ratio of successful hatchlings improves as the tortoise matures, then drops off again as the tortoise ages. Because of the difficulty in determining the age of a wild tortoise, there is little data on longevity, although many live for thirty years or more in captivity.

Food

Discussing the diet of the red-footed tortoise is difficult due to the wide variety of food it eats, the variety and seasonal availability of plants available across the extensive range, interpreting what field reports are trying to describe, and because studying fecal pellets gives very different results than what the animals are observed eating.

Forest-dwelling tortoises in the "Chelonoidis", "Indotestudo", "Manouria", and "Kinixys" genera are omnivores with upper and lower intestines of about the same length, while herbivorous genera such as "Gopherus" and "Testudo". have longer large intestines to digest fiberous grasses. Most omnivorous tortoises have no other specialized digestive structures, reflecting their generalized, flexible diet.

The bulk of the diet is some sort of fruit or seed pod. Common fruits come from cacti, figs, pehen, "Spondias", "Annona", "Philodendron", bromiliad, and more. Up to five different kinds of fruits are often found in fecal pellets. The entire fruit is eaten, and the seeds are passed and can germinate, giving red- and yellow-footed tortoises a significant role in seed dispersal. Red-footed tortoises have been observed at the base of fruit trees, apparently waiting for fruit to fall.

The rest of the diet includes grasses, leaves, flowers, roots, and shoots from a wide assortment of plants as well as fungi, live invertebrates, carrion, and feces. Tortoises are often found at carcasses feeding until gorged, and occasionally eat small live animals such as snakes and rodents. Pebbles and sand are also often found in fecal pellets.

The diet changes based on season and availability. In the wet season it may be roughly 70% fruit, 25% fresh leaves and shoots, and the rest being fungi and animal food. The dry season sees 40% fruits, 23% flowers, 16% fresh leaves and shoots, and the rest fungi, moss, and animal food.

Omnivorous tortoises will seek out foods high in calcium even if other foods are more readily available, and will even eat mineral-rich soil if they cannot get adequate calcium in the diet.Pet tortoises should be allowed to forage in a well-planted outdoor pen whenever possible. The basic diet should consist of a variety of plants, vegetables and fruits with occasional meat; and be high in calcium and fiber, and low in sugars and fats. Fruits should be kept as whole as possible. Commercial tortoise pellets can be offered along with fresh foods.

The bulk of the diet should be leafy greens such as turnip or collard greens, dandelion, leafy or curly lettuces, endive, kale, cabbage, edible tree or plant leaves such as mulberry or hibiscus, lettuce mixes, parsley, grape leaves, etc.

Vegetables and fruits offer variety and other nutrients, but are a smaller part of the captive diet. Good choices would include: cactus pads and fruits, papaya, figs, mango, mushrooms, pumpkin, squash, melon, pineapple, strawberry, cucumber, hays and grasses, corn, peas and beans, carrot, apple, pear, plums, and okra.

Meats form a very small part of the captive diet, and can include live bugs or invertebrates, baby mice or rats, chicken, egg, organ meat, lean beef, tuna or other 'oily' fish, or cat or dog food.

Calcium should be supplemented frequently in very small amounts. Other vitamins can be offered in very small amounts as well, but are best provided through a balanced, varied diet.

Predators

Hatchling and young tortoises are at high risk of predation. Tegu lizards, ring-tailed coatis, and introduced rats and mongooses attack nests and eggs. Many predators take the young tortoises, including large lizards, snakes, crocodilians, and even large turtles; predatory birds such as the curassow, guan, rails, cuckoos, and falcons; and mammals like cats, opossums, foxes, peccaries, and feral dogs.

Other than humans, the main predator of the adult tortoises are jaguars. Red-footed and yellow-footed tortoises seem to be a significant food source for jaguars in some parts of their respective ranges, such as Manú National Park in Peru. Jaguars will bite at the carapace and work at cracking or prying it apart to extract the soft tissues. Many tortoises show toothmarks from attacks that they survived, often on the hind end when they were otherwise protected in a burrow or shelter.