Aldabra tortoises, the second-largest land tortoises in the world, are fascinating creatures with unique dietary needs. Understanding their nutritional requirements is crucial for maintaining their health and well-being, whether in the wild or in captivity. This article provides a comprehensive overview of the Aldabra tortoise diet and nutrition, drawing on available research and practical experience.
Aldabra Tortoise Overview
Aldabra tortoises (Aldabrachelys gigantea) are endemic to the islands of Aldabra, a coral atoll that is part of the Seychelles, located northeast of Madagascar in the Indian Ocean. They were also introduced to Mauritius and Reunion Islands. These tortoises are known for their impressive size, reaching up to 550 pounds and living for over 100 years, possibly making them the longest-lived of all animals.
Their physical characteristics include:
- A thick, highly domed carapace that is dark grey to black. The carapace has a small neck plate that is usually visible, a feature absent in other species of giant tortoises.
- Thick, scaled limbs that are cylindrical and columnar like those of an elephant. The toes are short and two-jointed.
- A relatively small, pointed head covered by scales.
- Long necks, which help with food gathering.
- Males are considerably larger than females and have longer, thicker tails. The male's carapace length can measure 4 feet (1.22 meters), while the female's carapace can measure 3 feet (91 centimeters). The males have a concave plastron (belly shell) that aids in mating.
Aldabra tortoises inhabit a variety of habitats, including scrub, mangrove swamps, and coastal dunes. They are the largest animals on the Aldabra Island atoll and play a crucial role in their ecosystem, acting as the main consumers of vegetation and altering the habitat in their search for food. They have been known to knock over small trees and shrubs to obtain nutritious leaves. Seeds pass through the tortoise's digestive tract and eventually become food for many other species.
Dietary Habits in the Wild
In their natural habitat, Aldabra tortoises are primarily herbivorous, consuming a wide variety of vegetation. They are grazers and browsers, feeding mainly on grasses and woody plants. Their diet consists of leaves and grasses that provide them with sufficient amounts of fiber. They prefer to spend more time in areas with a high amount of calcium and other fundamental trace elements. They also supplement their diet with carrion, or the decaying flesh of animals, and may even eat the carcasses of dead tortoises. They may also eat feces.
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As the main consumers of vegetation on the island chain, Aldabra tortoises play a vital role in seed dispersal. They eat fruits, and the seeds pass through their digestive system, aiding in the propagation of various plant species.
Aldabra tortoises are able to go without food or water for long periods.
Nutritional Needs
A balanced nutrition is important for their health and welfare. Fundamentally, the main nutritional needs of Aldabra tortoise is a fibre and calcium rich diet. The Aldabra tortoise is a gut fermenting herbivore with a large fermenting gut. This adaptation in the gut increases its efficiency and ability to eat a high amount of fibre so a protein and fibre rich diet should be given to the tortoise in order to avoid any digestive problems or defects in feeding behaviour. Compared to mammals that subsist on a similar diet, tortoises have shorter gastrointestinal tracts.
To create a suitable diet formula, there are many aspects that ought to be understood, including but not limited to: nutritional requirements, the basic of food chemistry, the impact of environment on the species’ nutritional needs and an understanding of the importance and benefits of minerals and vitamins. Vitamins such as D3 and minerals such as calcium should be carefully mixed into their diet formula so as to prevent any defects which may put tortoise individuals at risk or to lead to their rapid suffering from deficiencies.
Generally, Aldabra tortoise’s diet should have a low amount of protein, fat, and phosphorus, while it should be high in fibre and calcium. As leafy green plants are rich in calcium, fibre, and minerals, they will form the fundamental part of Aldabra tortoises’ diets.
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Protein
In general, protein is a significant nutritional element for growth in juvenile tortoises. There are many circumstances that may occur as a result of protein deficiency such as disturbance in growth and weakness in reproduction. Diets of tortoises in the wild often contain > 15% protein (dry-matter basis) in plant materials consumed; natural vegetation is usually high in protein in the pre-seed stage, although a part of that protein is indigestible.
Roughage
Roughage has a positive effect on the motility of the intestinal tract of animals.
Vitamins
Many tortoises in captivity suffer from vitamin deficiency and that is due to restricted information which could help keepers decide which brand of vitamin-mineral to prepare that would be palatable by a tortoise. Daily requirements of the vitamin A are approximately 400 IU/kg body weight. Regarding the tortoises’ need of vitamin D3, there is no exact knowledge available, but compared to the hindgut-fermenting animals, the amount of vitamin D3 is estimated to be between 100 and 200 IU/ kg body weight daily. Folic acid is also important - especially in the creation of DNA and that could be provided through eating Alfalfa hay.
Calcium and Phosphorus
Calcium plays an important part in many metabolic processes in the tortoise’s body such as the metabolism of bone and the production of eggs. Compared with other species of tortoises, the nutrient requirement is measured as 2.0 % calcium and 1.2% phosphorus, and the ratio should be between 1:1 and 2:1. There are many sources from which could provide tortoises with an adequate amount of calcium, such as from cuttlefish bone and limestone flour because it contains roughly 38% of calcium.
Water
Aldabra tortoises should be provided with clean and fresh water. Tortoises living in areas with regular rainfall drink from puddles and leaves. If you live in areas with prolonged dry periods, offering them water helps to keep them hydrated. In our outdoor enclosures we make a small shallow cement pond (a few inches deep). The best water and food bowls for giant tortoises are large black tubs that are used to mix cement.
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Feeding Aldabra Tortoises in Captivity
Maintaining a healthy diet for Aldabra tortoises in captivity requires careful consideration of their nutritional needs and an understanding of the available food options.
Diet Composition
A captive diet should mimic their natural diet as closely as possible. The following components are essential:
- Grasses and Weeds: The tortoise needs to be eating grass and weeds. Grow pastures and put the tortoise out there to eat all day when weather permits. These should form the bulk of their diet, providing essential fiber and nutrients. Go to tortoise supply.com and oder the Testudo seed mix to grow and their Herbal Hay to sprinkle on. When I can't get weeds or leaves, I cut up heads of grocery store greens, mix in some calcium powder, soaked horse hay pellets, and one or more dried leaf options. A couple of days per week, I will add in some soaked lay crumbles, Mazuri LS, or soaked ZooMed pellets.
- Leafy Greens: Grocery store greens are not the best tortoise foods. They tend to lack fiber, calcium, and some of them have deleterious compounds in them. If you must use foods from the grocery store, favor endive and escarole as the main staples. Add in cilantro, arugula, collards, turnip and mustard greens, lettuces and many others for variety.
- Hay: Larger tortoises, such as Aldabra or Galapagos tortoises, can consume grass or alfalfa hay along with a complete pelleted food formulated for tortoises or exotic herbivores. Hay should be cut short, because the mouth shape of these tortoises makes it impossible for them to chew long-strand hay. You will also need to add some sort of amendment to improve the quality as tortoise food. Calcium is good to add a couple of times per week and soaked horse hay pellets are a good way to add fiber for any species. Pelletized hay products for horses. You can get a large variety of hays in pellet form from farm stores like Tractor Supply.
- Vegetables: A vegetable mix consisting of broccoli, green beans, leafy greens (eg, romaine, green leaf lettuce, endive), kale, and shredded carrots may be fed to supplement a formulated tortoise diet.
- Fruits: Cultivated fruits are typically poorer sources of protein, calcium, and micronutrients and, if fed in substantial amounts, vitamins and minerals should be added.
- Supplements: Calcium supplements are important, especially for young, growing tortoises and egg-laying females. Some herpetologists offer oyster shell and pea gravel to tortoises to dig and bury in, because “mining” activity has been observed in free-ranging animals.
- Commercial Diets: Small and large tortoises can be maintained on appropriately formulated extruded, pelleted, or coarsely ground tortoise diets. Soaked ZooMed tortoise pellets of any type are good to add, as is Purina Organic Lay Crumbles for chickens, oddly enough.
Here is a sample diet:Alfalfa hay (200 g), Orange with peel (100g), Apples with skin(200g), Melon with rind(100g), Grazer pellet (8.82g) , Moose pellet, Cabbage (50g), Chinese cabbage (100g), Dandelion leaves(100g), Yucca (50g), Lettuce (50g), Spinach (10g), Carrots (50g), pumpkin (20), Celery (100g), Pet cal, Vit E-cube, Vit D3, Vit A supplement to be between 300-400 , vitamin B12 supplement (1-1.5).
Feeding Frequency and Quantity
Overfeeding is a common problem encountered because tortoises prefer to be fed five to six times a week. Dry matter basis could provide Aldabra tortoises with 80% of their daily digestion and the nutrition approximates 1-4% of the tortoise weight daily.
Foods to Avoid
Avoid grocery store produce when possible. No bananas, ever. I would avoid the carrots too. They have a moderately high sugar content and they may be a bit of a choking hazard because of the way they snap. Don't Feed seeds, nuts, or avocado.
Hatchling Diet
Hello everyone, I have an aldabra hatchling around 262 grams. I am trying to figure out a feeding regimen. Anything I should add or leave out please let me know.
The tortoise needs to be eating grass and weeds. Grow pastures and put the tortoise out there to eat all day when weather permits. Avoid grocery store produce when possible. Grocery store greens are not the best tortoise foods. They tend to lack fiber, calcium, and some of them have deleterious compounds in them. If you must use foods from the grocery store, favor endive and escarole as the main staples. Add in cilantro, arugula, collards, turnip and mustard greens, lettuces and many others for variety. You will also need to add some sort of amendment to improve the quality as tortoise food. Calcium is good to add a couple of times per week and soaked horse hay pellets are a good way to add fiber for any species. Soaked ZooMed tortoise pellets of any type are good to add, as is Purina Organic Lay Crumbles for chickens, oddly enough.
Feed daily, enough that s/he can eat on and off all day. Add as much variety as possible. You can also try orchard grass hay. Cut it into smaller pieces and soak in water to soften a bit.
I am trying to get my sulcata hatchling started on some timothy/alfalfa pellets from tractor supply right away to get him used to the hay and starting have some minor success. I've been soaking them to a mush and just coating the various greens with the pellet mush so he basically has to eat it to get at what he really wants.
That's how you do it. I start with one broken small piece of one pellet for younger smaller tortoises.
You want horse hay pellets. Essentially this is just plain dry hay that has been shredded and macerated into tiny pieces and then compressed into a dry pellet. Over time, as the tortoise grows, add in more and more of the soaked pellets. Read the ingredients. It is best to feed your tortoise grass. When you can't do that for whatever reason, grass hay pellets are the next best thing. You can use grocery store greens and lettuce as a delivery vehicle for your soaked hay pellets and dried leaf mix-ins. Start slow with just one pellet. Gradually add more and more as your tortoise grows and begins to recognize the pellets as food.
Gut Health
Tortoises are herbivorous and, like herbivorous lizards, must consume plant material to maintain healthy gut physiology. Microbial fermentation of plant fiber can be a major nutrient source for tortoises.
Monitoring Growth
Young tortoises should be weighed regularly and should follow the growing curve to prevent too-slow or too-fast growth, which can cause permanent malformation of the carapace. Shell deformities in tortoises have been thought to result from rapid growth associated with consumption of high-protein diets. If outside. they never lose weight. I consider 2.5g slow and I look at what might be wrong. Let their stools be a guide. Their stool should be big and bushy, filled with hay and grass. If they are watery or you see diarrhoea you may be feeding too much fruit or “wet foods".
Additional Considerations for Captive Care
- Indoor vs. Outdoor Housing: Because of their size, adult Aldabra tortoises are best kept by those who have access to an outdoor area, where their tortoises can be kept for most, or all, of the year outdoors.
- Temperature and Lighting: Indoors, Aldabra tortoises can be maintained indoors 70 to 90 degrees. They should also have a basking area heated by an overhead light. This spot should be in the 92 to 98-degree range. Like most diurnal, herbivorous reptiles, they need a UVB light in their indoor enclosures to help them properly process the calcium in their diets. Keep lights on 12 to 14 hours a day, turn off all light sources at night.
- Enclosure Design: Aldabra tortoise enclosures require a sturdy wall at least 30-inches in height above ground, we use 4X4 post cemented in the ground with 3 levels of 2x8 pressure treated wood spaced every four feet. This is screwed (not nailed) together. You can also use concrete masonry blocks. These work well when cemented in place. There needs to be proper hide boxes or huts (for larger animals) accessible as a cool retreat during the summer months or a warm retreat during the winter.
Health Considerations
Common Health Problems
Aldabra tortoises can suffer from most common reptile health problems like intestinal parasites, (Protozoa, Strongyle worms, and in some cases Coccidia). Another common complication are respiratory infections if they are kept in cool or wet enclosures. The most common things that go wrong are diet, heat, light and poor cage conditions.
One other common complication baby Aldabras can get is constipation. Typically, this manifest itself as a little slime coming out of their mouth (not their nose.) or they typically go off food. One sign is they are not pooping and are acting lethargic. Constipation is typically caused by eating on a warm day then having a cold spell, which slows digestion.
Symptoms of respiratory stress and illness manifest as a runny nose, coughing and sneezing, runny eyes, respiratory noises or clicking. Coughing and sneezing sounds just like you would expect but coming from a tiny animal. Aldabra babies are also sensitive to allergies and irritants. Hay dust is an irritant that gives them runny eyes and sneezing.
Hygiene
Food bowl and water bowl cleanliness is important; clean with bleach or chlorine. Store bought chlorine sprays are fine or chlorhexidine is a great bacterial disinfectant but does not clean the way chlorine can. Remove old food before the end of day or if it becomes contaminated. Water bowels need to be disinfected and scrubbed with a bleach solution and rinse clean until the chlorine smell is gone. Be careful about irritating smells from disinfectants.
Parasites
Inspect the environment for ants, be careful to observe any ant hills or colonies. I use Amdro to treat ant hills; place the crystals in the mound and wet with a little water.
Conservation and Responsible Practices
Practice ecotourism by being an advocate for the environment when you’re on vacation. During your travels, support, visit or volunteer with organizations that protect wildlife. Shop smart too! Support organizations like the Smithsonian’s National Zoo and Conservation Biology Institute that research better ways to protect and care for this animal and other endangered species.