The Cross River gorilla is the most threatened of all gorilla subspecies. This primate population, estimated to be fewer than 300 individuals, is critically endangered and survives in a small, fragmented area along the border of Nigeria and Cameroon. Understanding what these rare great apes consume in their challenging environment is important for conservation efforts. The composition of their diet reflects the scarcity and seasonality of the resources available in their unique habitat.
The Core Diet: Primary Plant Matter
The majority of the Cross River gorilla’s diet throughout the year consists of high-fiber, low-nutrient plant materials. This reliance on tough vegetation provides sustenance when preferred, energy-rich foods are unavailable. This is a distinguishing feature of their feeding ecology compared to other gorilla subspecies.
They frequently consume the stems and piths of various herbs, which require significant processing to extract the soft, inner core. A notable staple is the ginger-like plant Aframomum, which gorillas peel to access the tender internal stem. They also incorporate a substantial amount of woody materials into their diet, including tree bark and liana.
Various types of foliage, or leaves, from different plant species also make up a large portion of their daily foraging. Gorillas are selective foragers, often consuming only specific parts of a plant, such as the roots, shoots, or a particular section of a stem.
Seasonal Foraging and Fruit Consumption
The Cross River gorilla’s diet is highly influenced by the dramatic seasonal shifts in their montane forest habitat. While fibrous vegetation is a constant, fruit is the preferred food item, driving significant changes in their foraging behavior. When fruits are ripe and abundant, they become the largest component of the gorillas’ meals, providing a much-needed energy boost.
The availability of fruit is patchy and requires the gorillas to travel longer distances to access these scattered, high-quality resources. During periods of fruit scarcity, which commonly occur around August to September and again from November to January, their diet shifts heavily back to terrestrial herbs, bark, and liana.
The wet season often brings a flush of new, nutritious shoots and leaves. Conversely, the dry season can promote the ripening of certain fruits, though overall resources become more challenging to find.
Unique Dietary Adaptations and Non-Plant Items
The Cross River gorilla exhibits several specialized feeding behaviors that allow them to utilize resources others might bypass. Their dental anatomy, featuring smaller mean cheek tooth surface areas compared to other gorillas, implies they specialize in consuming smaller, more manageable food items. They are adept at breaking down tough, fibrous plants to reach the soft tissues within.
To supplement their largely herbivorous diet, these gorillas also consume non-plant items, which provide essential minerals and protein. Observations confirm the occasional consumption of invertebrates:
- Snails
- Maggots
- Termites
- Caterpillars
These small additions are believed to be an important source of nutrients that are difficult to obtain from plant matter alone.
Less commonly observed, but documented, is the consumption of small vertebrates, such as a lizard. This flexibility in their diet ensures survival even when their preferred high-energy foods are unavailable.
Habitat Connection: Where Food is Found
The distribution of the Cross River gorilla’s food is intrinsically linked to the rugged, mountainous terrain they inhabit. Their territory spans various altitudes, from lower forest areas up to high-elevation zones, creating a mosaic of habitat types. This fragmented landscape means that food resources are not uniformly distributed and are often separated by steep slopes and valleys.
The gorillas must forage across these diverse and often challenging areas, which restricts their access to certain plants. Their diet is a direct reflection of the limited and patchy distribution of forest resources along the Nigeria-Cameroon border.
The need to find food in a highly seasonal and fragmented habitat is what drives their extensive knowledge of their territory. Their ability to switch between high-quality fruit and lower-quality fibrous fallback foods is a necessary strategy for survival in an environment with unpredictable resource availability.