Grazers by nature, tortoises love to chew on weeds, flowers, and grasses. What about spinach? Is this green leafy vegetable a safe food for tortoises?
The truth is that tortoises can eat some spinach as part of a varied diet.
Spinach is high in oxalic acid, which can interfere with calcium absorption. Since tortoises need lots of calcium to remain healthy, foods high in oxalic acid should be limited.
Can Tortoises Eat Spinach?
Yes, most tortoises can eat spinach in moderation. Tortoises thrive on a weed-based diet (which can include certain veggies). Most importantly, their diet should have variety.
Tortoises are natural grazers, so they mostly eat weeds and grasses, like:
- Dandelions.
- Sowthistle.
- Chicory.
- Hedge mustard.
- Plantains.
- Honeysuckle.
Ideally, grow tortoise-safe weeds at home, and these would make up the bulk of your pet’s diet.
In addition, veggies like broccoli, cauliflower, parsnip, cucumber, and spinach can make up a small part of your tortoise’s diet.
That said, spinach has some harmful components that must be acknowledged.
Spinach Nutritional Information for Tortoises
Few foods are good or bad, but some are more nutritious.
Spinach is interesting because it has some benefits but also some troublesome components. Let’s start by looking at the beneficial components of spinach for tortoises:
- Vitamin C – According to The Tortoise Table, vitamin C is rapidly depleted under stress.
- Vitamin A – This is needed for a healthy mouth, gut, and lungs.
- Vitamin E – This is important for a healthy immune system.
Now, let’s move on to the slightly more negative things about spinach:
- The calcium-to-phosphorous ratio isn’t optimal.
- It’s high in oxalic acid.
- It’s high in thiocyanates.
Let’s explore why these components might cause problems for a pet tortoise, especially when spinach is consumed in excess.
Why Is Spinach Bad for Tortoises?
Spinach is potentially bad for tortoises because it could lead to nutrient deficiencies (calcium deficiency) and metabolic disorders (metabolic bone disease, hypothyroidism).
Calcium-To-Phosphorous Ratio
As mentioned, spinach could be bad for tortoises because its calcium-to-phosphorous ratio is approx. 2:1.
This is problematic because, according to Meridian, the natural diet for most tortoises is a calcium-to-phosphorus ratio of 4:1 or even 5:1.
This means that a natural diet for tortoises is much higher in calcium than phosphorous.
If a tortoise eats too much phosphorus (and too little calcium), it’ll struggle to regulate the calcium in its blood, which may result in hypocalcemia.
This unnatural calcium-to-phosphorous ratio isn’t a concern when feeding spinach to your tortoise in small amounts. However, feeding too much spinach to your tortoise could create metabolic problems.
High in Oxalic Acid
Spinach is high in oxalic acid, and it’s thought that tortoises can’t readily absorb calcium oxalate (the oxalic acid in spinach), so they don’t receive much calcium from eating spinach.
Not only that, but the oxalic acid might bind to any free calcium in the tortoise’s gut, further impeding calcium absorption.
It’s important to say that there hasn’t been much research looking into the effects of oxalic acid on reptiles, and some argue that it’s speculation rather than a proven problem.
Nevertheless, some veterinary journal articles published by T and F online DO make the connection between spinach and calcium disorders.
For example, the above article recommends reducing spinach (and other high oxalate veggies) as a food source if a tortoise’s calcium levels dip too low.
Why Is Low Calcium A Problem?
If your tortoise can’t absorb enough calcium, it’ll be vulnerable to hypocalcemia (low blood calcium). This is also referred to as “soft shell disease” according to Vet Lexicon and creates symptoms like:
- Lethargy/weakness.
- Spongy shell and body.
- Refusing food/drink.
- Eventual death.
That said, spinach (and other high oxalate veggies) should never be fed as a primary food source because calcium is vital for tortoise health.
Spinach is High in Thiocyanates
According to Mag Online Library, spinach is high in “thiocyanates” (a compound found in potassium and other minerals). High levels of thiocyanates may cause hypothyroidism in tortoises.
However, only two small studies have shown potential evidence, so we don’t have enough information to say whether thiocyanates harm tortoises.
How Much Spinach Can Tortoises Eat?
Spinach isn’t something you should give your tortoise daily. According to Tortoise Den, veggies should be an “occasional” food source for tortoises.
Once a week, mostly during the winter, would be an appropriate frequency for feeding spinach to your tortoise. In terms of portion size, offer your tortoise 2-4 leaves.
Are There Any Tortoises That Shouldn’t Eat Spinach?
Most tortoises can eat a small amount of spinach. A few tortoise species eat more fruit than leaves/stems (Red-Footed tortoise, yellow-footed tortoise, and Elongated tortoise). These tortoises are more likely to enjoy fruit as a supplement to their diet rather than veggies.
It’s a good idea to exercise extra caution when feeding a:
- Female tortoise as she reaches reproductive age.
- Hatchlings – up to 4 years old.
Tortoises at the above stages of life need sufficient calcium to grow strong, so you wouldn’t want to risk a dietary imbalance at this stage. If you feed your tortoise spinach (and other high oxalate veggies), ensure the diet has enough calcium.
Is My Tortoise Getting Enough Calcium?
Most nutrients don’t work in isolation but rather in tandem.
In the case of calcium, vitamin D3 is needed. Sunlight (UVB rays) help tortoises to create vitamin D3, so if your tortoise isn’t getting sunlight and a good-quality UV lamp, it may be at risk of calcium deficiency.
You can also supplement with vitamin D3, although sunlight or UV light is usually considered a preferable source of vitamin D3.
Another way to increase calcium uptake is to dust food with a good quality calcium powder and provide cuttlefish for your tortoise to chew on.
Key Takeaways
The most important word to remember for optimum tortoise health is “variety.” Tortoises enjoy grazing on a range of (safe) grasses, weeds, flowers, and some veggies/fruits
Spinach is fine to give to tortoises, but it must be given in small amounts (2-4 leaves, about once a week)
Your tortoise may prefer spinach, but it’s important not to overfeed your tortoise its favorites.
There’s a risk that too much spinach (and other high-oxalate veggies) can interfere with calcium absorption. You can moderate this risk by ensuring your tortoise gets enough calcium.
Be mindful of your tortoise’s calcium intake since calcium is vital for tortoise health.
