Species group: Map Turtles
Other common names: Delta Map Turtle
Scientific name: Graptemys nigrinoda
The Black-Knobbed Map Turtle’s has one of the smallest ranges of any North American Turtle, being restricted to the Alabama, Tombigbee and Black Warrior River Systems in Alabama and Mississippi, USA. It is also a habitat specialist, being found only in sand or clay-bottomed streams with moderate currents and numerous fallen logs and brush piles. Largely aquatic, this turtle spends much time basking on logs, plunging into the water when disturbed. The Black-Knobbed Map Turtle feeds only in water, and, except when nesting, rarely travels far from shore.
Appearance / health:
Beauty, rarity and small size render this species as one of the most sought after of all turtles. The olive-brown carapace is topped by high, black, knob-like projections (as you might expect!), heavily serrated along the edges and bears circular yellow or orange marks…truly a unique and beautiful creature. Even the plastron is attractive, being yellow with a reddish tint and bearing the thin black “map-like” lines that give this turtle and its relatives their common name. Smaller than most map turtles, the Black Knobbed tops out at 4-6 inches in length.
Behavior / temperament:
Black-Knobbed Map Turtles are not as hardy as related species (and much more expensive!), and are best reserved for experienced turtle-keepers. Although somewhat shy, most adjust well to captivity, but they may not become as responsive as other map turtles. All turtles are capable of administering powerful bites and scratches when frightened, and must be handled with care. Black-Knobbed Map Turtles can be aggressive towards other turtles, and must be watched carefully if housed in groups. Males should not be kept together, as they will usually fight.
Due to their small size, Black Knobbed Map Turtles are more easily-accommodated than most of their relatives. However, they are active swimmers, and do not take well to close confinement. A 30-55 gallon aquarium should be provided. Bare-bottomed enclosures are preferable, as gravel greatly complicates cleaning. The aquarium should be equipped with a dry basking site, UVB bulb, heater, and powerful filtration. Ambient water temperature: 72-80 F; Basking temperature: 90-95 F
Turtles are messy feeders, and quickly foul even well-filtered aquariums. Removing your pet to a plastic storage container at feeding time will lessen the filter’s workload and help to maintain good water quality. Partial water changes (i.e. 50 % weekly) are also very useful. Filters designed specifically for turtles, if serviced regularly, are usually preferable to those marketed for use with tropical fish. Some folks find it easier to maintain their aquatic turtles in plastic storage containers that can easily be emptied and rinsed.
Limited field studies indicate that Black-Knobbed Map Turtles feed primarily upon insects and snails. Pets should be offered a diet comprised largely of whole animals such as minnows, shiners, earthworms, snails, crayfish, prawn, butter worms, roaches, crickets and other insects Goldfish should be used sparingly, if at all, as a steady goldfish diet has been linked to kidney and liver disorders in other turtle species. A high quality commercial turtle chow can comprise up to 50% of the diet. A cuttlebone should be available to supplement the calcium provided by whole fishes and similar foods.
Captive breeding is sporadic, with a typical clutch, usually deposited in June, consisting of only 3-7 eggs. Gravid (egg-bearing) females usually become restless and may refuse food. They should be removed to a large container (i.e. 5x the length and width of the turtle) provisioned with 6-8 inches of slightly moist soil and sand. Gravid females that do not nest should be seen by a veterinarian as egg retention invariably leads to a fatal infection (egg peritonitis). It is important to note that females may develop eggs even if unmated, and that captives may produce several clutches each year. The eggs may be incubated in moist vermiculite at 82-86 F for 60-75 days.
Written by Frank Indiviglio