HIGH PEP PLANTS DESERT TORTOISES SEEK AND NEED
WHY GROCERY PRODUCE & COMMERCIAL PELLET PRODUCTS CAN BE
VERY HARMFUL, ESPECIALLY IN EXCESS
Desert tortoises have evolved/adapted to exist and thrive on a high fiber, low
carbohydrate diet that is mainly only high in protein in the early spring when new growth
of annuals is available, dependent on winter rainfall. Observations and studies of their
plant selection in the wild has made it clear that when available, they will select the
majority of their diet from plants that may only constitute a very small percentage of the
available plant biomass of their area. Captive desert tortoises fed high protein, low fiber,
high carbohydrate diets are often afflicted with various types of MBD (Metabolic Bone
Disease) , bladderstones and weakened immune systems. The below may help clarify a
specific need often negated by captive diets.
High PEP (Potassium Excreting Potential) means the plants have low potassium levels and excess potassium can be toxic to desert tortoises. In order to excrete excess potassium, they need
adequate water and protein in the form of nitrogen from their diet to bind it in uric acid crystals and excrete it (unlike desert iguanas who can “cry” potassium salt tears!).
Most high PEP plants are spring annuals and are especially important to baby tortoises,
who require the provision of surplus protein and water above that needed for potassium
excretion. They are very important for growth of shell, muscle and other protein
containing organs which represent nutrient reservoirs to be drawn upon during prolonged
food shortages caused by droughts. (Baby tortoises can often be observed in warm
winter spells when they can sun and warm enough to digest foods foraging for early
spring annual growth during wet winters while it is still small, before the adults awaken).
(Jennings, Berry, Nagy, Oftedal, Morafka, Boarman, Avery, Esque, Hillard, etc. etc.)
Grocery produce is more often than not fertilized with chemicals Nitrogen, Potassium
and Phosphorus (NPK) which can inhibit normal processes in healthy growth (yes, even
many “organic grown”). The potassium will cause increased need for water and protein
and the phosphorus can bind up calcium so it is unavailable for bone/shell/tissue growth.
Additionally there are often pesticide residues which studies have shown are difficult (if
not impossible) to wash off and if unhealthy for humans, has to be for tortoises that
weigh 1/10th to 1/20 a normal humans’ weight.
Factor in that most produce is “engineered” sweeter for human taste/consumption and
you have a reversal of the desert tortoise requirement for high fiber, low sugar foods and thus
will require much more water, possibly stressing kidneys (Highfield).
Commercial tortoise pellets are often composed of oats, corn, soy, wheat middlins and
multiple chemicals (often containing Vitamin D3), in the main being higher carbohydrate
and lower in fiber and again, will require much more water. Even the newer, “better”?
products composed mainly of grasses are very short fibers, chemically supplemented and
will require more water as they tend to move through the digestive system rapidly vs.
slow transit time of higher, longer fiber native graze items.
Growing natural graze diet plants initially takes more effort, but when established is easy to maintain, healthier for our tortoises and provides more enjoyment observing them graze rather than eat from
a food dish.
Please see Plants and Foods link for general diet guidelines.