The Effect of Rodent Granivory on Recruitment of the Irregularly Fruiting Podocarpus falcatus in the Southern Cape

Abstract

SYNOPSISRodent granivory was investigated at four Podocarpus falcatus trees after a fruiting season during which huge amounts of seeds were produced. Feeding stations were established from one metre from the base of the trees to at least six metres beyond the edge of the seed shadow. No significant correlations were found between the density of seed on the ground and the number of seeds destroyed at the feeding stations. The major granivore was identified as Verreaux's mouse Praomys verreauxii and it is concluded that it forages randomly and not in a density dependent manner.

Fifteen years of annual Cape ParrotPoicephalus robustuscensuses: current population trends and conservation contributions

“…The occupancy of forest patches by Cape Parrots has remained largely the same for nearly half a century, except for some forests along the escarpment, as mentioned earlier. This suggests that the absence of Cape Parrots in some forests during certain periods are not local extinctions, but is likely due to the absence of food, as the fruiting of their preferred yellowwoods may be sporadic and absent in some years (Silvertown 1980;Koen 1991;Wirminghaus et al 2001c;Hart et al 2013). During the years when yellowwoods do not fruit, the parrots feed on other forest fruit and often have to fly between forests to source these (Skead 1964;Wirminghaus et al 2001bWirminghaus et al , 2001cWirminghaus et al , 2002bDowns 2005a).…”

“…(Skead 1964;Wirminghaus et al 2001bWirminghaus et al , 2001cWirminghaus et al , 2002bDowns 2005a), which are typically only available from June through to November (Wirminghaus et al 2001c(Wirminghaus et al , 2002b. Yellowwood trees are mast fruiting, which is the intermittent but synchronous production of large numbers of fruits by a population of trees (Silvertown 1980;Koen 1991;Wirminghaus et al 2001c;Hart et al 2013). These fruiting events can be separated by long intervals of 6-7 years (Geldenhuys 1993).…”

Reproductive biology and population structures of Podocarpus falcatus and P. latifolius in southern Cape forests

“…During normal years of relatively small seed output, all P. f a l c a h s seed are destroyed (C. J. Geldenhuys, personal observations). Koen (1991) recorded predation levels of 66% by the rodent Praomys verreauxii over a 10-month period (December 1987 to September 1988), during a mast year for P. falcatus. He calculated that, theoretically, a P. verreauxii individual could feed on about 5000 P. falcatus seeds over 1 year, and six to seven rodents, as were recorded during the study, could destroy the total seed crop at each tree during years of low seed production.…”

“…were collected in small numbers in the forest (G. J. Breytenbach, personal communication, 1989), and destroyed 66% of the seeds in situ (the species does not remove seed to its nesting place) during a mast year in 1987 (Koen, 1991). Phillips ( 1926, 193 1) reported dispersal of the seed by bushpig but small pieces of sclerotesta in pig faeces during good seed years rather indicate that pigs totally destroy the seed.…”

Reproductive biology and population structures of Podocarpus falcatus and P. latifolius in southern Cape forests

“…The endosperm of Podocarpus is rich in nutrients, especially oil and starch (Coertze, 1966;Osborn, 1960). During mast years the few mammalian seed predators in the southern Cape forests (Koen, 1991) are quickly satiated of the abundant seed (see also Beveridge, 1964;Travers, 1961) and therefore predate the seed less effectively. Koen (1991) recorded predation levels of 66% by the rodent Praomys verreauxii over a 10-month period (December 1987to September 1988, during a mast year for P. falcatus.…”