Distribution and status of the hippopotamids in the Ivory Coast

Fecal standing crop counts along line transects are an established method for difficult-to-observe ungulates, including the pygmy hippo.

“Relative population densities were estimated by performing fecal standing crop counts along line transects, an established method for difficult-to-observe ungulates (Barnes, 2001; Hoppe-Dominik et al., 2011), including the pygmy hippo (Roth et al., 2004).”

Debate remains regarding the exact nature and strength of the relationship between the pygmy hippo and open bodies of water, particularly the relative importance of different types of aquatic habitats.

“Similarly, debate remains regarding the exact nature and strength of the relationship between the pygmy hippo and open bodies of water, particularly with respect to the relative importance of different types of aquatic habitats (Conway, 2013; Roth et al., 2004).”

Variation in vegetation structure may influence pygmy hippo density on a local scale.

“While the pygmy hippo has traditionally been viewed as rather flexible in terms of habitat selection within the rainforest (Roth et al., 2004), recent work has indicated that variation in vegetation structure may influence their density on a local scale (Ouattara et al., 2019; Rijkers, 2024).”

The Djouroutou research zone is among the most densely inhabited areas known anywhere today for pygmy hippos.

“Our population density estimate of 4.2 pygmy hippos per km 2 places the Djouroutou research zone among the most densely inhabited areas known anywhere today (Hoppe-Dominik et al., 2011; Roth et al., 2004), reaffirming the conservation value of research zones in West Africa, as Kely et al. (2021) already noted for the forest elephant.”

The main threats to the pygmy hippopotamus include habitat fragmentation, land conversion and hunting.

“The main threats to the species include habitat fragmentation, land conversion and hunting (Roth et al., 2004).”

Average home range for C. liberiensis is estimated to be 0.4-0.5 km2 for females and 1.5 km2 for males.

“Average home range for C. liberiensis is estimated to be 0.4-0.5 km 2 for females and 1.5 km 2 for males (Roth et al., 2004).”

Pygmy hippopotami are known to inhabit the protected areas within their range.

“There are 87 protected areas covering 30 669 km 2 that are partially or totally located inside the pygmy hippopotamus's range (UNEP-WCMC & IUCN 2021), and pygmy hippopotami are known to inhabit them (Roth et al. 2004, Collen et al. 2011, Garteh 2013, Conway et al. 2015, Bogui et al. 2016, Hillers et al. 2017, Ouattara et al. 2018).”

There may be habitat for c. 2,000 female and fewer than c. 600 male pygmy hippopotamus across Sierra Leone and Liberia.

“This indicates there may be habitat for c. , female and fewer than c.  male pygmy hippopotamus across the two countries.”

The northernmost extent of C. liberiensis in Côte d'Ivoire is the area around Mt. Nimba in the upper Cavally River valley.

“The northernmost extent of C. liberiensis in Côte d'Ivoire is the area around Mt. Nimba in the upper Cavally River valley (Roth et al. 2004).”

Estimates of 0.8-2.5 C. liberiensis per km2 of suitable habitat were extrapolated to generate abundance data for Taï National Park plus buffer zones: 12,000 in 1982; 5,000 in 1997.

“Estimates of 0.8-2.5 per km 2 of suitable habitat were extrapolated to generate abundance data for Taï National Park plus buffer zones: 12,000 in 1982; 5,000 in 1997 (Roth et al. 2004).”

The size of wild C. liberiensis populations remains unknown but is widely considered to be declining based on the evidence of continued habitat loss and reduced densities reported for Côte d'Ivoire.

“The size of wild populations remains unknown but is widely considered to be declining based on the evidence of continued habitat loss and reduced densities reported for Côte d'Ivoire (Roth et al. 2004;Hoppe-Dominik et al. 2011).”

Variables contributing to potential inaccuracy in population estimates include the inability to discern individual animals, the skill of detecting footprints and droppings, the decomposition rate of feces, and defecation rates.

“Variables contributing to potential inaccuracy include the inability to discern individual animals from camera trap footage or footprints, the skill of detecting footprints and droppings, the decomposition rate of the feces, and defecation rates (Bülow 1987;Roth et al. 2004).”

Population estimates for C. liberiensis range from 2,000 to 3,000 worldwide to possibly as many as 15,000 for Côte d'Ivoire alone.

“Population estimates range from 2,000 to 3,000 worldwide (Eltringham 1993(Eltringham , 1999;;Ransom et al. 2015) to possibly as many as 15,000 for Côte d'Ivoire alone (Roth et al. 2004).”

The analyses could be compromised by the fact that male and female home ranges can overlap, suggesting that two different individuals could have contributed to each sampling location.

“Finally, these analyses could be compromised by the fact that male and female home ranges can overlap, suggesting that two different individuals could have contributed to each sampling location (Roth et al., 2004).”