Kagu (Rhynochetos jubatus): revise global status?

The enigmatic Kagu (Rhynochetos jubatus) is endemic to New Caledonia (to France), occurring primarily in forest habitats. Its restricted and severely fragmented range means that it has been considered Endangered, although this may now require revision. Population trends had previously been considered to be declining as a result of habitat degradation (e.g. Chartendrault and Barré 2005, 2006), and mortality caused by introduced species such as cats, rats, pigs, and dogs as well as from hunting (Hunt et al. 1996, Y. Létocart in litt. 1999, J. Theuerkauf in litt. 2007, S. Rouys in litt. 2008).

However, for some time now (at least since the 2008 Red List assessment) the population trend has been considered to be stable. Field surveys by Chartendrault and Barré (2005, 2006) confirmed that kagus are still found in most of the areas previously surveyed by Hunt in 1992, and with decreasing hunting activity in many areas, birds are being able to recolonise places they had previously been extirpated from (R. Gula and J. Theuerkauf in litt. 2012). Population surveys in the key areas for this species have shown an increasing population in Parc Grandes Fougères, and a fluctuating population in Parc Provincial Rivière Bleue, though the population at this site may be stable over the long term (J. Theuerkauf in litt. 2016).

Further, the Extent of Occurrence (EOO) of this species has been recalculated using a Minimum Convex Polygon to strictly follow IUCN guidelines (IUCN 2001, 2012, Joppa et al. 2016), and this newly calculated EOO means the species may no longer meet the threshold for Endangered under any Red List Criterion. Therefore, given this information the species has been re-assessed against all criteria using current information.

 

Criterion A – As the population is currently considered to be stable and there is no quantified evidence of a reduction over the last three generations, it would not warrant listing as threatened under this criterion.

 

Criterion B – The newly calculated EOO for this species is 7,400km2. This falls in the range for Vulnerable under criterion B1. Analyses from Tracewski et al. (2016) calculated the amount of available forest in 2012 (a proxy for the Area of Occupancy) for this species to be c.1,070km2, which would fall in the range for Vulnerable under criterion B2. The species’ range is considered to be severely fragmented, yet forest loss has been very low (c.0.67% over 3 generations [45 years]; extrapolated from data for 2000-2012) (Tracewski et al. 2016). However, it may be conservative to consider the quality of habitat to be decreasing as introduced deer may damage forests (Chartendrault and Barré 2005, 2006), and pigs may disturb the forest floor (although Ekstrom et al. [2002] suggest that pigs may cause only minimal impacts on Kagu). Therefore, the species may warrant listing as Vulnerable under criteria B1ab(iii)+2ab(iii), although if the currents impacts on habitat quality are deemed minimal it may not warrant listing as threatened under this criterion.

 

Criterion C – The population in Parc des Grandes Fougères is suspected to be >250 adults, and potentially >1,000 individuals overall (J. Theuerkauf in litt. 2016); 500 individuals are suspected to occur in Parc Provincial Rivière Bleue (J.-M. Mériot in litt. 2007, J. Theuerkauf in litt. 2016); and 491 mature individuals are thought to occur elsewhere in its range. It is uncertain what proportion of the 500 individuals in Parc Provincial Rivière Bleue are mature and so the population size is conservatively considered to be <1,000 mature individuals. This is sufficiently low to meet the threshold for Endangered under this criterion. However, the sub-population structure means it would not meet the sub-population structure conditions for Endangered (meeting those for Vulnerable instead), and the fact that the population is now considered to be stable means that the species would not warrant listing as threatened under criterion C.

 

Criterion D – The population size estimate of <1,000 mature individuals means that the species meets the threshold for Vulnerable under criterion D1.

 

Criterion E – No quantitative analysis of extinction risk has been carried out for this species to the best of our knowledge. Therefore, it cannot be assessed against this criterion.

 

Therefore, it is proposed that Kagu be listed as Vulnerable under criteria B1ab(iii)+2ab(iii); D1. As the population trend has been considered to be stable for at least 5 years then we are unable to use the 5 year rule to pend a downlisting of this species; and even if there were evidence to suggest that the population trend was decreasing overall this would only result in a change in criteria string to Vulnerable under criteria B1ab(iii,v)+2ab(iii,v); C2a(i); D1. Thus to retain the species as Endangered would require evidence of smaller range or sub-population sizes.

Comments on this proposal are welcome, though please note that this topic is not designed to be a general discussion about the ecology of the species, rather a discussion of the species’ Red List status. Therefore, please make sure your comments are about the proposed listing.

 

References

Chartendrault, V.; Barré, N. 2005. Etude du statut et de la distribution des oiseaux menacés de la Province Nord de Nouvelle-Calédonie. Institut Agronomique néo-Calédonien, New Caledonia.

Chartendrault, V.; Barré, N. 2006. Etude du statut et de la distribution des oiseaux des forêts humides de la province Sud de Nouvelle-Calédonie. Institut agronomique néo-calédonien, Port Laguerre, Nouvelle-Calédonie.

Ekstrom, J. M. M.; Jones, J. P. G.; Willis, J.; Tobias, J.; Dutson, G.; Barré, N. 2002. New information on the distribution, status and conservation of terrestrial bird species in Grande Terre, New Caledonia. Emu 102: 197-207.

Hunt, G. R.; Hay, R.; Veltman, C. J. 1996. Multiple Kagu Rhynochetos jubatus deaths caused by dog attacks at a high-altitude study site on Pic Ningua, New Caledonia. Bird Conservation International 6: 295-306.

IUCN. 2001. IUCN Red List Categories and Criteria: Version 3.1. IUCN Species Survival Commission. IUCN, Gland, Switzerland and Cambridge, U.K.

IUCN. 2012. IUCN Red List Categories and Criteria: Version 3.1. Second edition. IUCN Species Survival Commission. IUCN, Gland, Switzerland and Cambridge, U.K. Available at: www.iucnredlist.org/technical-documents/categories-and-criteria.

Joppa, L. N.; Butchart, S. H. M.; Hoffmann, M.; Bachman, S. P.; Akçakaya, H. R.; Moat, J. F.; Böhm, M.; Holland, R. A.; Newton, A.; Polidoro, B.; Hughes, A. 2016. Impact of alternative metrics on estimates of extent of occurrence for extinction risk assessment. Conservation Biology 30: 362-370.

Tracewski, Ł.; Butchart, S. H. M.; Di Marco, M.; Ficetola, G. F.; Rondinini, C.; Symes, A.; Wheatley, H.; Beresford, A. E.; Buchanan, G. M. 2016. Toward quantification of the impact of 21st-century deforestation on the extinction risk of terrestrial vertebrates. Conservation Biology 30: 1070-1079.

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2 Responses to Kagu (Rhynochetos jubatus): revise global status?

  1. According to the definition of the IUCN Red List Categories and Criteria (Version 3.1) “mature individuals that will never produce new recruits should not be counted”, “in the case of populations with biased adult or breeding sex ratios, it is appropriate to use lower estimates for the number of mature individuals”, and “where the population size fluctuates, use a lower estimate”. All these 3 points apply in the case of the Kagu, therefore the Kagu warrants being listed as endangered under the criterion C2a(i) as it is unlikely that any subpopulation contains continuously 250 mature individuals.
    Due to its unique social organisation with cooperative breeding (Theuerkauf et al. 2009) and skewed sex ratio (Theuerkauf et al. 2018), only about half of mature individuals are breeding. Besides, only about half of the population is mature (Theuerkauf et al. unpublished data), resulting in only about one fourth of Kagu being breeders. Therefore, only a subpopulation of 1000 individuals represents a subpopulation with 250 mature individuals as defined in the IUCN criteria. The only subpopulation that reached this number for a short time (less than 5 years) lives in the Parc des Grandes Fougères. However, the population suffered a major population reduction caused by 2 dogs within 2 months in 2017 killing 50% of radio-tagged individuals, which resulted in destruction of over 75% of Kagu families. Such predation events by stray dogs are regular, making it unlikely that any subpopulation will be able to reach 250 mature individuals in the future. The only reason why some subpopulations of Kagu survived is that dogs have not (yet) established wild populations in New Caledonia but are associated with human settlements (Rouys and Theuerkauf 2003). This threat will rather become more important in the future, if dogs establish wild populations (see the example of the Dingo in Australia) or human settlements spread (current annual human population growth in New Caledonia is about 2%).
    All Kagu research has pointed towards the critical role of dog predation in Kagu survival. Only three populations have been monitored so far in New Caledonia. Hunt et al. (1996) monitored the population of the Pic Ningua for a few months until dogs killed 86% of the 21 radio-tagged Kagu and most of the population. Intensive monitoring of 10 Kagu families in the Parc Provincial de la Rivière Bleue in 2002-2012 by our research team (Gula et al. 2010, Theuerkauf et al. 2009, 2015, 2017, 2018) revealed a observed population reduction in the Parc de la Rivière Bleue of about 20% every 4 years, corresponding to a 50% reduction in 10 years. One of these 20% reductions was caused by only 1 dog present for 6 weeks in the park. We described above the heavy reduction in the third monitored population of the Parc des Grandes Fougères. These 3 populations are among the best preserved populations as in the two parks dog are managed, therefore we expect that most other populations suffer much higher predation rates by stray dogs.
    Besides, it is possible that the Kagu warrants also the status endangered concerning criterion B2a,c. Tracewski et al. (2016) estimated the amount of available forest for the Kagu to be 1,070 km². The area of occurrence might however be lower than 500 km² as we observed that only about half of suitable forests are actually colonised by Kagu and each time there is a predation event, the area of occurrence shrinks (Theuerkauf et al. unpublished data). Kagu can be seen occasionally in other habitats than forest, but these areas cannot be counted as area of occurrence as they are sink habitats. Even in forest, not all families with established territories reproduce. One family living in rainforest of the Parc Provincial de la Rivière Bleue had for example no successful breeding attempt in over 10 years of monitoring (Theuerkauf et al. unpublished data). The reason is that most subpopulations of Kagu live in refuge habitats on ultramafic soils rich in heavy metals (Theuerkauf & Gula 2018), which are suboptimal habitat, in which reproductive output of Kagu is very low (Theuerkauf et al. 2017). This is because areas of better habitat, such as the Parc des Grandes Fougères, are closer to human settlements, exposing Kagu to predation by dogs. Predation by dogs is probably also the reason why the Kagu population is fragmented. Our current genetic analysis based on microsatellite markers (Stoeckle et al. 2012) indicates that there is little genetic exchange between populations. We think therefore that the Kagu needs to keep it present status as endangered species.
    Jörn Theuerkauf and Roman Gula

  2. Hannah Wheatley (BirdLife) says:

    Preliminary proposal

    Based on available information, our proposal for the 2018 Red List would be to pend the decision on this species and keep this discussion open until 2019, while leaving the current Red List category unchanged in the 2018 update.

    Final 2018 Red List categories will be published on the BirdLife and IUCN websites in November, following further checking of information relevant to the assessments by both BirdLife and IUCN.

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