Papers by Katarzyna Nowak
Live-capture of animals is a widely used technique in ecological research, and previously trapped... more Live-capture of animals is a widely used technique in ecological research, and previously trapped individuals often respond to traps with either attraction or avoidance. The effects of trapping on animals' risk perception are not often studied, although nonlethal effects of risk can significantly influence animals' behavior and distribution. We used a combination of experimental (giving-up densities: GUDs) and behavioral (vigilance rates) measures to gauge monkeys' perceived risk before and after a short livetrapping period aimed at ear-tagging monkeys for individual recognition as part of ongoing research. Two groups of arboreal samango monkeys, Cercopithecus albogularis schwarzi, showed aversion to capture in the form of generalized, group-level trap shyness after 2 individuals per group were cage trapped. We predicted that trapping would increase monkeys' antipredatory behavior in trap vicinity and raise their GUDs and vigilance rates. However, live-capture led to no perceptible changes in monkeys' use of space, vigilance, or exploitation of experimental food patches. Height above ground and experience with the experiment were the strongest predictors of monkeys' GUDs. By the end of the experiment, monkeys were depleting patches to low levels at ground and tree heights despite the trapping perturbation, whereas vigilance rates remained constant. The presence of cage traps, reintroduced in the final 10 days of the experiment, likewise had no detectable influence on monkeys' perceived risk. Our findings, consistent for both groups, are relevant for research that uses periodic live-capture to mark individuals subject to long-term study and more generally to investigations of animals' responses to human interventions.
Wild species use habitats that vary in risk across space and time. This risk can derive from natu... more Wild species use habitats that vary in risk across space and time. This risk can derive from natural predators and also from direct and indirect human pressures. A starving forager will often take risks that a less hungry forager would not. At a highly seasonal and human-modified site, we predicted that arboreal samango monkeys (Cercopithecus albogularis labiatus) would show highly flexible, responsive, risk-sensitive foraging. We first determined how monkeys use horizontal and vertical space across seasons to evaluate if high-risk decisions (use of gardens and ground) changed with season, a proxy for starvation risk. Then, during a subsequent winter, we offered equal feeding opportunities (in the form of high-value, raw peanuts) in both gardens and forest to see if this short-term change in food availability and starvation risk affected monkeys’ foraging decisions. We found that during the food-scarce winter, monkeys foraged outside indigenous forest and in gardens, where they fed on exotic species, especially fallen acorns (Quercus spp.), despite potential threats from humans. Nevertheless, and as predicted, when given the choice of foraging on high-value foods in gardens vs. forest during our artificial foraging experiment, monkeys showed a preference for a safer forest habitat. Our experiment also indicated monkeys’ sensitivity to risk in the lower vertical strata of both habitats, despite their previous extensive use of the ground. Our findings support one of the central tenets of optimal foraging theory: that risk of starvation and sensitivity to the variation in food availability can be as important drivers of behavior as risk of predation.
Humans and human infrastructure are known to alter the relationship between predators and prey, t... more Humans and human infrastructure are known to alter the relationship between predators and prey, typically by directly or indirectly shielding one of the species from the other. In addition to these overt changes to animals' behavior, observers may have more subtle impacts on animals' foraging decisions. However, the anthropogenic alteration of risk-taking behavior has rarely been acknowledged or quantified, particularly in behavioral ecological studies reliant on habituated animals. We tested the magnitude of the "human shield effect" experimentally on 2 groups of samango monkeys, Cercopithecus mitis erythrarcus, at a site with high natural predator density and no human hunting pressure. In general, giving-up densities-the density of food remaining in a patch when a forager leaveswere greatest at ground level (0.1 m) relative to 3 tree canopy levels (2.5, 5, and 7.5 m), highlighting a strong vertical axis of fear. When human followers were present, however, giving-up densities were reduced at all 4 heights; furthermore, for 1 group, the vertical axis disappeared in the presence of observers. Our results suggest that human observers lower monkeys' perceived risk of terrestrial predators and, thereby, affect their foraging decisions at or near ground level. These results have significant implications for future studies of responses to predation risk based on habituation and observational methods.
Swamp forests may be important refuges for primates and felids where these taxa are threatened wi... more Swamp forests may be important refuges for primates and felids where these taxa are threatened with habitat loss. Mangrove and peat swamp forests, impenetrable, wet habitats, inaccessible and uninhabitable for humans, may, in some regions, be the most significant remaining habitats for threatened species. They are nevertheless neglected in field studies compared to relatively species-rich, terrestrial tropical forests probably, in part, because of the difficulties associated with surveying them. As a result, maps of mammal distributions may overlook swamp forests although camera-trapping is gradually rec tifying this gap. I have compiled and mapped records of over 60 primate and 20 felid taxa reported to use mangrove and peat swamp forests in Africa and Asia at 47 sites, of which 21 are Afrotropical mangrove, 25 are Indo-Malayan mangrove or peat swamp forest, and 1 is an outlying mangrove site in Japan. Eleven of these are designated Ramsar Sites. I highlight key sites of conservation priority on the basis of primate and felid species richness and composite 'threat scores'. Petit Loango in Gabon and Gunung Palung National Park in Indonesia emerged as top priority sites in Africa and Asia, respectively. Further research on the role of swamp forests in the ecology and persistence of threatened mammals is needed.
An increasing number of fi eld studies on behavioral adaptations and learning suggest that a capa... more An increasing number of fi eld studies on behavioral adaptations and learning suggest that a capacity for fl exibility in local responses to disturbance could buffer some so-called specialists against that disturbance. We discuss how specialization, rather than an intrinsic species trait, appears to be moderated by fl exible and learned behavior and may not represent a useful trait in comparative analyses of extinction vulnerability. Furthermore, the use of primate species as indicators of the effects of disturbance on communities needs to be balanced with data on their capacity to adjust behaviorally. We present recent examples of innovative and fl exible behavior in primate taxa, some of which have traditionally been viewed as highly specialized, for example species of red colobus. We also highlight research gaps in the ecological specialization-behavioral fl exibility domain.
We censused two discrete subpopulations of the endangered Zanzibar red colobus (Procolobus kirkii... more We censused two discrete subpopulations of the endangered Zanzibar red colobus (Procolobus kirkii) and sympatric Sykes's monkeys (Cercopithecus mitis albogularis) between February 2004 and September 2005 in two coastal forests in Zanzibar, including the northernmost (Kiwengwa-Pongwe Forest) and some of the southernmost (Uzi and Vundwe Islands) extents of P. kirkii's range. Surveys totalled 365 hours and 307.8 km along >16 km of line transects; 472 sightings were made (Red colobus n = 252; Sykes's monkey n = 220). The southern forests (coral rag with adjacent mangrove) of Uzi and Vundwe Islands were found to support P. kirkii at a higher estimated density (29.6 groups/km²) relative to the northern coral rag forest (lacking mangrove) in Kiwengwa-Pongwe (7.5 groups/km²). However, for red colobus in coral rag, up to c.40% of these "groups" could be "sub-groups" based on our observations of consistent fission-fusion and small groups seen during the census (6.63 ± 0.4SE in Kiwengwa, 6.64 ± 0.33SE in Uzi) and behavioral follows in this habitat type. We therefore also include density estimates expressed as individuals/km² (49.72 individuals/km² in Kiwengwa, 196.32 individuals/km² in Uzi). On Uzi and Vundwe Islands, colobus densities were higher than those of Sykes's monkey (Sykes's monkey density = 18.9 groups/km²), while we found no difference between the density of these two taxa in Kiwengwa (Sykes's monkey density = 8.1 groups/km²) where encounters with humans were more frequent, vegetation was more disturbed, and the two species often associated. Although these populations represented a fraction of the historical total population of red colobus and Sykes's monkeys on Zanzibar, their estimated abundance was significant, and their marginal habitat and unprotected status were important in the general context of primate conservation in unprotected and fragmented landscapes.
Priority Primate Areas are identified in Tanzania, mainland Africa's most important country for c... more Priority Primate Areas are identified in Tanzania, mainland Africa's most important country for conservation of primates, on the basis of occupancy by globally rare, Red-Listed and range-restricted primate species and subspecies.
Swamp forests may be important refuges for primates and felids where these taxa are threatened wi... more Swamp forests may be important refuges for primates and felids where these taxa are threatened with habitat loss. Mangrove and peat swamp forests, impenetrable, wet habitats, inaccessible and uninhabitable for humans, may, in some regions, be the most significant remaining habitats for threatened species. They are nevertheless neglected in field studies compared to relatively species-rich, terrestrial tropical forests probably, in part, because of the difficulties associated with surveying them. As a result, maps of mammal distributions may overlook swamp forests although camera-trapping is gradually rec tifying this gap. I have compiled and mapped records of over 60 primate and 20 felid taxa reported to use mangrove and peat swamp forests in Africa and Asia at 47 sites, of which 21 are Afrotropical mangrove, 25 are Indo-Malayan mangrove or peat swamp forest, and 1 is an outlying mangrove site in Japan. Eleven of these are designated Ramsar Sites. I highlight key sites of conservation priority on the basis of primate and felid species richness and composite 'threat scores'. Petit Loango in Gabon and Gunung Palung National Park in Indonesia emerged as top priority sites in Africa and Asia, respectively. Further research on the role of swamp forests in the ecology and persistence of threatened mammals is needed.
Cycads and colobus monkeys occur together in many parts of tropical Africa; we present the first ... more Cycads and colobus monkeys occur together in many parts of tropical Africa; we present the first records of colobus feeding on these plants. On 22 occasions, the Endangered Zanzibar red colobus Procolobus kirkii fed on the leaves of Encephalartos hildebrandtii, a Near Threatened species, in the Kiwengwa-Pongwe Forest Reserve, north-eastern Unguja. A total of 92 minutes of cycad feeding were observed during a 14-month, 678-hour study of three focal groups, suggesting rare but consistent use of cycads. We analyzed HCN content in a small sample of browsed and unbrowsed cycad leaves for a preliminary analysis of toxicity, but toxicity was similar (and high) across leaves. Colobus appear to be one of the few mammal species able to exploit this abundant food source (277 cycads/ha) in the 33 km2 coral rag forest. Both colobus and cycads of this region are in need of urgent protection; in August 2011, much tree cutting was observed resulting in a discontinuous canopy which will threaten the arboreal colobus and shade-germinating cycads.
American Journal of Primatology, Jan 1, 2008
Isolated populations of Procolobus kirkii on Uzi Island, Zanzibar, use Rhizophora mucronata domin... more Isolated populations of Procolobus kirkii on Uzi Island, Zanzibar, use Rhizophora mucronata dominated mangrove forest for refuge. Three groups, observed over 14 months, spent up to 85% of total observation time in mangroves with brief excursions to adjacent upland coral rag forest, habitat degraded by human cutting. A large proportion of monkeys’ diets consisted of plant parts of five mangrove species. Water drinking was common and 326 water-drinking events were recorded at a rate of up to 0.87 drinks/hr. Groups used different strategies to obtain water including licking dew, drinking from treeholes, licking rain off leaves and tree trunks, and drinking from coral rock crevices with Cercopithecus mitis albogularis. Drinking frequency increased with time spent in and consumption of mangroves. Strategies for obtaining water were group-specific and likely the result of learning. Drinking appeared to be an acquired behavior in movement-restricted groups living in a habitat with low plant species diversity and limited salty foods.
International journal of primatology, Jan 1, 2008
We investigated the role of geographical insularity in divergence and speciation of Procolobus ki... more We investigated the role of geographical insularity in divergence and speciation of Procolobus kirkii by examining cranial morphology. The sample (n= 369) included museum specimens of Procolobus spp. and recently deceased individuals of P. kirkii from the main island of Zanzibar and 2 smaller islands in the archipelago. Geometric morphometrics evinced pronounced divergence of Procolobus kirkii from mainland Procolobus, including members of P. badius ssp., P. pennantii ssp., P. rufomitratus, P. gordonorum and also representatives of the assemblage of red colobus populations from Central Equatorial Africa. Procolobus kirkii has a small cranium, consistent with the island rule for large mammals, reduced sexual dimorphism consistent with Rensch’s rule, and a distinct cranial form. Analyses of phenotypic variance of Procolobus kirkii gave no evidence for population bottlenecks in the history of the species, but there is a clear indication that the species has experienced accelerated morphological evolution of size, probably as a result of insularity. Their highly distinctive morphology lends weight to the argument that they are a unique insular endemic species in need of active conservation.
International Journal of Primatology
More than half of the global population of the endangered Zanzibar red colobus Procolobus kirkii ... more More than half of the global population of the endangered Zanzibar red colobus Procolobus kirkii live outside the one major protected area on Zanzibar Island. We present data on the two largest, discrete subpopulations living in unprotected areas at extremes of the species’ range. We compare the size and structure of 11 groups, specifically six core groups inhabiting interior, mature forest with five peripheral groups living in disturbed / degraded edge habitats. Groups living in southern mangrove forest – a species-poor but more productive and less seasonal habitat than coral rag thicket – had larger group sizes, more heterogeneous age structure, were more stable and had higher rates of infant survival than did groups in northern coral rag. Group size ranged from 5.5 ± 1.6 S.D. (the smallest reported for this species) in edge coral rag to 31.2 + 1.9 S.D. in core mangroves. Edge groups were significantly smaller than core groups in northern coral rag while in the south, where all groups had access to mangroves, we found no significant difference in mean group size between edge and core areas. Groups using mangroves exhibited frequent social play, an indicator of habitat quality, and had a higher ratio of births per female per year. We suggest that mangroves are an important refuge and possibly source habitat for Zanzibar red colobus. We urge the conservation of mangrove and remaining coral rag in the unprotected areas described here in an effort to sustain this endemic species throughout its range.
Books by Katarzyna Nowak
SUMMARY Roads in East Africa present unique challenges to wildlife conservation because reserves ... more SUMMARY Roads in East Africa present unique challenges to wildlife conservation because reserves are largely unfenced and biodiversity is high. Few roads in the region carry high‐speed, high‐volume traffic, but this is changing rapidly. This chapter reviews existing research on the impact of roads on East African wildlife, research needs and mitigation strategies. Road type and protected area status affect the direct impacts of roads and traffic on wildlife in East Africa. Indirect impacts of East African roads may be even more important than the direct impacts. Documenting remaining movements and migrations in these rapidly changing landscapes is critical. Mitigation of road impacts on East African wildlife has mostly relied on low‐cost approaches.
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Papers by Katarzyna Nowak
Books by Katarzyna Nowak