How practitioners integrate decision triggers with existing metrics in conservation monitoring.

Decision triggers are defined thresholds in the status of monitored variables that indicate when to undertake management, and avoid undesirable ecosystem change. Decision triggers are frequently recommended to conservation practitioners as a tool to facilitate evidence-based management practices, but there has been limited attention paid to how practitioners are integrating decision triggers into existing monitoring programs. We sought to understand whether conservation practitioners' use of decision triggers was influenced by the type of variables in their monitoring programs. We investigated this question using a practitioner-focused workshop involving a structured discussion and review of eight monitoring programs. Among our case studies, direct measures of biodiversity (e.g. native species) were more commonly monitored, but less likely to be linked to decision triggers (10% with triggers) than measures being used as surrogates (54% with triggers) for program objectives. This was because decision triggers were associated with management of threatening processes, which were often monitored as a surrogate for a biodiversity asset of interest. By contrast, direct measures of biodiversity were more commonly associated with informal decision processes that led to activities such as management reviews or external consultation. Workshop participants were in favor of including more formalized decision triggers in their programs, but were limited by incomplete ecological knowledge, lack of appropriately skilled staff, funding constraints, and/or uncertainty regarding intervention effectiveness. We recommend that practitioners consider including decision triggers for discussion activities (such as external consultation) in their programs as more than just early warning points for future interventions, particularly for direct measures. Decision triggers for discussions should be recognized as a critical feature of monitoring programs where information and operational limitations inhibit the use of decision triggers for interventions.

When and why do territorial coalitions occur? Experimental evidence from a fiddler crab.

Neighboring territory owners are often less aggressive toward each other than to strangers ("dear enemy" effect). There is, however, little evidence for territorial defense coalitions whereby a neighbor will temporarily leave his/her own territory, enter that of a neighbor, and cooperate in repelling a conspecific intruder. This is surprising, as theoreticians have long posited the existence of such coalitions and the circumstances under which they should evolve. Here we document territorial defense coalitions in the African fiddler crab Uca annulipes, which lives in large colonies wherein each male defends a burrow and its surrounding area against neighbors and "floaters" (burrowless males). Fights between a resident and a floater sometimes involve another male who has left his territory to fight the floater challenging his neighbor. Using simple experiments, we provide the first evidence of the rules determining when territorial coalitions form. Our results support recent models that suggest that these coalitions arise from by-product mutualism.

The fiddler crab Uca mjoebergi uses colour vision in mate choice.

Although the role of colour in mate choice is well known, few tests of colour vision have been based on mating behaviour. Females of the fiddler crab Uca mjoebergi have recently been shown to use claw coloration to recognize conspecific males. In this study I demonstrate that the females use colour vision for this task; preferentially approaching yellow claws over grey claws regardless of their intensity while failing to discriminate between yellow claws differing in intensity. This is one of only a handful of studies confirming the involvement of colour vision in mate choice and the first conclusive evidence in fiddler crabs.

Visually mediated species and neighbour recognition in fiddler crabs (Uca mjoebergi and Uca capricornis).

Mating signals are often directed at numerous senses and provide information about species identity, gender, receptiveness, individual identity and mate quality. Given the diversity of colourful body patterns in invertebrates, surprisingly few studies have examined the role of these visual signals in mate recognition. Here, we demonstrate the use of claw coloration as a species recognition signal in a fiddler crab (Uca mjoebergi). Furthermore, we show that distinct carapace colour patterns in Uca capricornis enable males to discriminate between their female neighbours and unfamiliar females. This is the first empirical evidence of the social importance of colour markings in fiddler crabs and the first example of visually mediated species and neighbour recognition in invertebrates other than insects.

Colouration and colour changes of the fiddler crab, Uca capricornis: a descriptive study.

Colour changes in animals may be triggered by a variety of social and environmental factors and may occur over a matter of seconds or months. Crustaceans, like fiddler crabs (genus Uca), are particularly adept at changing their colour and have been the focus of numerous studies. However, few of these studies have attempted to quantitatively describe the individual variation in colour and pattern or their adaptive significance. This paper quantitatively describes the colour patterns of the fiddler crab Uca capricornis and their ability to change on a socially significant timescale. The most dramatic changes in colour pattern are associated with moulting. These ontogenetic changes result in a general reduction of the colour pattern with increasing size, although females are more colourful and variable than similarly-sized males. Uca capricornis are also capable of rapid colour changes in response to stress, but show no endogenous rhythms associated with the semilunar and tidal cycles commonly reported in other fiddler crabs. The extreme colour polymorphism and the relative stability of the colour patterns in Uca capricornis are consistent with their use in visually mediated mate recognition.