Guinea-Bissau is host to the westernmost subpopulation of the common hippopotamus Hippopotamus amphibius, which is one of only two known populations inhabiting coastal waters. The presence of hippopotamuses causes conflict with rice farmers as a result of crop damage and the absence of effective measures to protect crops. To develop an effective method for protecting rice fields, we studied the patterns of access to flooded and rain-fed rice fields by hippopotamuses and assessed the effect of the installation of electric fences. Hippopotamuses were detected in 54% of the flooded fields (n = 100) and in 31.9% of the rain-fed fields (n = 91). They were detected more frequently in fields on offshore islands than on the mainland, in unfenced than in fenced fields, and in fields closer to running water. Hippopotamuses entered fenced flooded fields less frequently than unfenced, and were detected most frequently at the end of the rainy season and the start of the dry season, and in the period of vegetative stem growth. Electric fences were an effective deterrent and facilitated increased rice production. The maintenance and cost of the electric fencing were acceptable to farmers, and therefore the use of such fencing is recommended to resolve the conflict between hippopotamuses and farmers in Guinea-Bissau and in other areas with similar conditions.

The population dynamics of the red swamp crayfish (Procambarus clarkii Girard, 1852) was studied from May 2005 to May 2006 in a pond (PCD) subjected to drought between June and December and in a continuously flooded rice field drainage channel (PMG) located in the Tejo river basin, Portugal. The proportion of females in the population was not independent from the season and was negatively correlated with both female and male maturation status. Male and female maturation was synchronous but males remained in a reproductive form after recruitment while females reverted quickly to lower maturation indexes. At PCD and PMG, respectively 2 and 5 cohorts were detected by modal analysis. Large crayfish were abundant in spring, summer and early autumn and juveniles were abundant in autumn, especially at PCD. Crayfish density at PCD was lower than at PMG and mortality rate (Z) was 3.99 at PCD and 2.43 at PMG. The average lifespan of the crayfish populations was 91 days at PCD and 150 days at PMG. Our study indicated faster growth and larger maximum sizes at the site with the more stressed environment and lowest relative crayfish densities (PCD), suggesting that any exploitation or control strategies for these two populations should consider management of the hydroperiod and of maximum crayfish densities.

Indicators of diversity (population density, relative number of species and evenness) in ground beetles (Carabidae) and rove beetles (Staphylinidae) in upland rice fields were assessed between 1995 and 1999 at Garoua in the Benue valley in North Cameroon. A total of 4369 beetles belonging to 45 carabid species and 2109 beetles belonging to 31 staphylinid species were caught in pitfall traps. Among the carabid beetles, five species Scarites (Orientolobus) lucidus strigiceps Quedenfeldt, Chlaeniostenus denticulatus elatus (Erichson), Lissauchenius venator (LaFerté), Pheropsophus marginatus (Dejean) and Abacetus crenulatus Dejean, in decreasing order, were dominant. In the staphylinid group, Paederus sabaeus Erichson was the most common, followed by Stenus ravus Puthz and Stenus (Mendicus) senegalensis Bernhauer. The Shannon–Weiner and evenness indices varied slightly from year to year. Diversity values remained relatively low among the staphylinid beetles, revealing that rice fields were underpopulated by this group of polyphagous predators. The features of predatory soil-surface beetles and the role they play as an IPM component in West African rice ecosystems are discussed.