Medium sized herbivores

This group comprises all herbivorous (including omnivorous) species with a weight ranging from 5 to 100 kg, which were found to damage crops in at least one of our study areas (Chapter 7, Table 1). Although smaller in size, this group of species must not be disregarded due to its strong destructive potential. Rodents, for example, were mentioned as the species group causing the most damage to farms in northern Tanzania, compared to elephants, hyenas, lions or jackals and were, therefore, the group of species most desirable to decrease (Bencin et al. 2016).

7.3.1 Crop damages by medium sized herbivores

Although medium sized herbivores accounted for a larger proportion of less severe damage of below 40% of the total farmed crops by one farmer (Chapter 2, Table 1), they caused the same mean cost of damage as elephants and other large herbivores in the Asian study areas (Chapter3, Fig. 2). Exceptionally high costs of crop damage by medium sized herbivores found in the RS in BA, exceeding those of crop damage by elephants, are due to damage caused by wild boar and spotted deer (Chapter 3).

Wild boar (S. scrofa) and other suids are well known for their potential to damage crops in a wide geographical range (Ballari and Barrios-García 2014; Byg et al. 2017; Herrero et al. 2006). In my study I found them damaging crops in all four study areas. Wild boar and bushpigs (P. larvatus) are opportunistic feeders consuming browse, grasses, roots, barks, insect larvae and even scavenge (Ballari and Barrios-García 2014; Breytenbach and Skinner 1982), whereas warthogs (P. africanus) are specialized grazers, plucking grass and feeding on grass rhizomes (Botha and Stock 2005; Cumming 2013). As all three species also feed on the underground parts of plants, they intensively search the soil for food and rooting plants (Chapter 7, Plate 6A-D). This rooting behaviour, as well as wallowing in crop lands, can cause heavy damage, destroying crop fields completely (Li et al. 2012). In SL and TA, bushpigs and warthogs were found to damage maize and groundnuts, exclusively. This agrees with the findings of Seydack (2013), who mentioned bushpigs extensively damaging maize, groundnuts, sugar cane and beans on agricultural fields and of Vercammen and Mason (1993), who reported warthogs damaging groundnuts in the DR Congo. In MA, only rice was damaged by wild boar, but in BA a wide variety of over nine crop species including potatoes,

other vegetables and fruits, were damaged. Bleier et al. (2016) found that wild boar damaged maize increasingly throughout the growing season and were probably influenced by the appearance of the corncobs. This finding is supported by our study, as boar/hogs preferred harvested crops to crops at an intermediate stage of growth. The risk of crop damage by wild boar has also been found to increase with closer proximity to the forest edge and rivers (Saito et al. 2011). The availability of cover to hide close to crop fields (Ficetola et al. 2014; Li et al.

2012), or even a buffer close to the wooded areas where hunting is banned (Amici et al.

2011), seems to foster crop damage by suids. In contrast, overground openness or the low cover of urban areas, as well as human population density, and short distances to roads, reduce the likelihood of suids damaging crops (Saito et al. 2011). It has to be mentioned that only a few studies rely on data obtained from damaged fields, with the objective calculation of losses. Many studies use secondary data, recorded for payment of compensation, or interviews with farmers (Pandey et al. 2016). The perception that suids are the most severe wildlife pest, may be influenced more by their generalist and destructive feeding behaviour, than by the costs of damage they cause; Linkie et al. (2007), regard wild boars as a species blamed for more crop damage than they actually cause.

Less obvious crop damage was found to be caused by smaller deer and antelope species. Spotted deer (A. axis) as well as impala antelope (A. melampus), are moderately sized and relatively light in weight (Table 1). Both species are mixed feeders, feeding on both grasses and browse to varying proportions; browse being consumed during the dry season and freshly re-growing grasses during the rainy season (Cerling et al. 2003; Khan 1994). The spotted deer occurs over a very wide range including the lowland forests of Nepal and throughout India, Bhutan, Bangladesh and Sri Lanka, in many large sub-populations (Duckworth et al. 2015). In Manas national park, the population of spotted deer had been decreased substantially in the 1980s, although a first new sighting was registered in January 2017 (Goswami 2017). The impala are found widely in the woodlands and savannahs of southern and eastern Africa (Fritz and Bourgarel 2013). Both, spotted deer and impala can graze in large groups, however, crop damage may not be obvious at a first glance, as they chew or nibble some specific parts of the plant (Bayani et al. 2016). In my study, spotted deer and impala preferred visiting farms with crops in the green and soft intermediate growth stage and before the dry season. Spotted deer in BA mainly fed on lentil, mustard and wheat, an observation that is supported by findings from Nepal and India, where crop damage by spotted deer was reported as being high, with animals feeding on rice, wheat, maize, mustard and lentils (Karanth and Nepal 2012; Studsrod and Wegge 1995; Thapa 2010). Despite their

presence in SL, impala in our study only caused crop damage in TA. Here, they fed exclusively on beans in great quantities (Chapter 7, Plate 5E&F); this is consistent with their diet, including pods of Acatia spp., being high in protein (Fritz and Bourgarel 2013). Impala have not been mentioned as a major crop pest from other African countries. In Uganda, however, they have been found feeding on maize and millet (Tweheyo et al. 2012).

Although primates occur in all four study areas and are frequently observed close to villages, they were found to cause relatively few damages, mainly in SL, in this study. Here, yellow baboons (P. cynocephalus) and vervet monkeys (C. pygerythrus) preferred to feed on maize, similar to the situation in Kibale national park, Uganda, where primates have caused big losses to farmers; olive baboons (P. anubis) preferred consuming maize, whereas red-tailed monkeys (Cercopithecus ascanius Audebert) damaged sweet banana (Naughton-Treves 1998). From this study, it is known that young boys are kept out of school, to guard crops against baboons during the daytime, resulting in a low literacy level amongst boys (Mackenzie et al. 2015). In the Cape Peninsula, South Africa, chacma baboons (Papio ursinus Kerr) have become accustomed to feeding on human food sources, such as fruit, sugar and bread from waste areas or houses in rural and urban environments (Kaplan et al. 2011); this is a situation well known in many Indian towns and cities, where rhesus macaques (Macaca mulatta Zimmermann) live from scavenging waste food around markets and offerings at temples (Priston and McLennan 2013). The low frequency of recorded crop damage by primates in our study areas may have been due to underreporting, as damage caused by a few individuals or small troops may not be easily visible.

In my study porcupines (Hysterix spp.) mainly caused crop damage in SL, with a very low frequency and comparably less severe damage. Due to their destructive behaviour while uprooting crops, they have been compared to bushpigs in Uganda (Kagoro-Rugunda 2004). In Nepal, the porcupine has been mentioned as a less frequent crop damaging species (Karanth and Nepal 2012).

Plate 6: Pictures of typical damages by medium sized herbivores on crop fields: (A) and (B) Wild boar footprint on rice field and damage of rice in intermediate stage of growth in MA, (C) and (D) bushpig footprints and damage of maize in SL, (E) and (F) impala foot print and damage to beans TA.

Pictures taken by Awely Red Caps.

7.3.2 Crop protection against small herbivores

Protecting crop fields from suids has been attempted in many areas with different levels of success. In Japan, weeding around rice paddies, electric fencing and corrugated iron fencing have been effective at reducing damage by wild boars (Saito et al. 2011), although electric fencing in Switzerland has not achieved the desired results (Geisser and Reyer 2004). In China, the guarding of fields at night has shown positive effects (Li et al. 2012). However, especially in Europe, the reduction of wild boar populations through hunting has been seen as the only effective way to reduce crop damage by this species (Bobek et al. 2017; Geisser and Reyer 2004).

In case of spotted deer and impala, chasing them away with loud sounds and drumming was found to be relatively easy, however, animals would return once no sounds were heard anymore (Thapa 2010; Tweheyo et al. 2012). Fencing with wire mesh or the planting of natural barriers of dense vegetation was found to be effective for spotted deer, provided these barriers were high enough, as the deer are able to challenge fences of a height of 1.5 meters by jumping over them (Bayani et al. 2016; Karanth and Nepal 2012; Thapa 2010). Impala, famous for their characteristic and high jumps were found to be excluded by barriers higher than 2.5 meters (Staver et al. 2014).

In our study, the only protection measure that showed a significant effect of cost reduction for medium sized herbivores compared to non-protected fields, was through electric fencing in BA. Interestingly, this fence had been set up against elephants and was met with some doubt (Chapter 3), but it seems to have provided some protection against both wild boar and spotted deer. As both species forage in larger groups, I assume that some group members did not cross the fence or were alerted due to the fence, which may have made them move onwards.

Primates, as being diurnal, were not targeted by nocturnal guarding activities and easily overcame any barrier found in the four study areas. To deter them from fields, specific guarding activities during the daytime need to be carried out (Kaplan et al. 2011; Mackenzie et al. 2015). Porcupines generally played a lesser role in crop damage in all study areas.