Barbara Vuillaume

Background: Hidden Markov models (HMMs) are increasingly used to infer animal behavioural states from GPS tracking data, yet their interpretation often remains uncertain in the absence of empirical validation. Misinterpretation of statistical states as biologically meaningful behaviours can undermine scientific understanding and conservation decisions. Our objective was to evaluate how well HMM-inferred states correspond to directly observed behaviours and to test how the temporal resolution of GPS sampling influences behavioural inference. Methods: We used GPS collars equipped with video cameras to validate HMM-inferred behavioural states in 81 female migratory caribou ( Rangifer tarandus ) from two herds. We compared states derived from two- and three-state HMMs to behaviours observed in short collar video clips. To assess the effect of temporal scale, we fit HMMs to GPS data resampled at 20-, 60-, and 120-minute relocation intervals. Results: HMM-inferred behavioural states frequently diverged from video-observed behaviours at the start of observed GPS steps, especially at longer relocation intervals. These mismatches appeared to result from overlapping movement metrics among caribou behaviours (e.g., foraging vs. resting or traveling) and the inability of coarser GPS data to capture behavioural switches occurring at finer temporal scales than the fix rate. Videos of eating were the most misaligned with HMM-inferred states, likely due to high variation in caribou movement while foraging that is often characteristic of mixed-feeding large herbivores. Inferred states for a given location were often inconsistent across temporal scales, indicating that HMM outputs must be interpreted cautiously with respect to the GPS sampling frequency. Conclusions: The predicted HMM state can differ substantially from true behaviour at the start of each step, in particular at coarse temporal scales. Our results serve as a reminder to interpret HMM states over whole steps rather than at observed positions, validate movement-derived states where possible, and align sampling resolution with species-specific behavioural patterns.

To develop effective management to maintain or restore populations of large herbivores, wildlife managers require sound empirical data on their variations in size and associated parameters. Many studies have highlighted links between morphological traits of individuals and population density; however, less attention has been devoted to whether or not morphological traits can reliably inform on population size in years when no population estimates are available. We evaluated the relationships between three morphological traits (hind foot length, body mass, and body fat) and population size interpolated over three decades, for four migratory caribou (Rangifer tarandus) herds in northern Canada and Alaska. Our sample included 8865 measurements of 4473 individuals. We used a Bayesian modeling approach to evaluate the relationships between morphology and population size across different sex and age classes, considering different temporal scales and, when possible, phases of population growth or decline. We found that morphological traits were not consistently linked to population size. Statistically significant relationships existed for some combinations of herd and age classes, but weak to absent relationships were more common. Our study suggests that morphological traits alone cannot replace data obtained from aerial surveys to approximate population size when population trends are unknown. We discuss the usefulness of morphological traits to explain population size, and recognize their role as complementary metrics to inform the management and conservation of large herbivores, but conclude that morphological data should not be used to predict population size without information on population trends.

Migratory caribou (Rangifer tarandus) is a socioeconomically and culturally key species for northern communities in the Arctic, and most of its populations are experiencing a sharp decline. Female migratory caribou depend on the availability of summer habitat resources to meet the needs associated with lactation and the accumulation of fat reserves to survive when resources are less abundant. Because of the large scales at which habitat and resource data are usually available, information on how female migratory caribou select habitat and resources at fine scales in the wild is lacking. To document selection of summer feeding sites, we equipped 60 female caribou with camera collars from 2016 to 2018. We collected a total of 65,150 10-sec videos between June 1^st and September 1^st for three years with contrasted spring phenology. We determined the selection at the feeding site scale (3^rd scale of Johnson) and food item scale (4^th scale of Johnson) using resource selection probability functions. Wetlands were highly selected as feeding sites in June and July while they were avoided in August. Shrublands were mostly selected in July and August. At the resources scale, lichen, birch, willow, and mushrooms were the most strongly selected resources. Our results provide precise and novel information on habitat selection at feeding sites and food resources selected by female caribou in the wild. This information will help understand foraging patterns and habitat selection behavior of female migratory caribou and will contribute to the management and conservation of its declining populations.

The decline of most caribou (Rangifer tarandus) populations underlines the need to understand the determinants of key demographic parameters. In migratory caribou, we have limited information on rates and drivers of pre-weaning mortality. We fitted 60 pregnant females of the Rivière-aux-Feuilles caribou herd with GPS camera collars to track the survival of calves from birth to weaning in 2016–2018. Over the three years, calf survival rate before weaning, i.e. to 01-Sep, approximately three months of age, was 0.63 (CI 0.50–0.77). Summer mortality risk was mainly influenced by calf birth date, with calves born earlier in the calving season having a lower mortality risk than those born later. Mortality also increased when calves experienced low or high temperature during calving. This study provides the first estimates of pre-weaning survival of migratory caribou calves in this herd, illustrating the value of new technologies to collect data otherwise difficult to obtain in widely distributed migratory populations. This approach can easily be extended to other large herbivores and predators. Our study brings new insights on how climate change may affect summer juvenile survival given the increased temperatures and faster changes in plant phenology expected in the future.

Monitoring survival of juveniles in wild populations of vertebrates is challenging because capture and marking of neonates may influence survival and induce biases. Camera collars have proven effective in resource and habitat selection studies, but their effectiveness to assess offspring survival is unknown. Our objective was to monitor the survival of neonates using camera collars installed on 24 preparturient female migratory caribou ( Rangifer tarandus ) of the Rivière‐aux‐Feuilles herd, from 2016 to 2018, in Nunavik, Canada. Females were captured with a net gun fired from a helicopter and pregnancy was confirmed by ultrasound. Cameras recorded a 10‐second video every 20 min from 1 June until 1 September 2017, when the collar detached automatically. We used Cormack‐Jolly‐Seber models to assess survival and resighting probabilities of calves based on their observation in the videos. Three collars failed, recording less than 30% of the expected videos, including one on a female that did not give birth. Among the 21 females wearing a functional collar, one gave birth to a stillborn calf. We analyzed 25,820 videos recorded from 20 collars. Calf sightings in videos were less frequent as the monitoring period advanced, but we estimated the probability of observing a live calf at 0.77 (SE = 0.42) over the sampling period. Videos indicated a survival rate of 0.67 (SE = 0.11) from birth to 1 September. Our results suggest that camera collars installed on adult females can be used to reliably assess offspring survival, and thus improve our understanding of caribou population dynamics. The application of camera collars should be useful for other large vertebrate species for which the assessment of neonate survival is lacking or difficult to obtain. © 2021 The Wildlife Society.

The Lesser Antilles, in the Eastern Caribbean, were long considered to have only two species in the genus Iguana Laurenti 1768: the Lesser Antillean iguana Iguana delicatissima, which is endemic to parts of the Lesser Antilles, and the Common green iguana Iguana iguana, which also occurs throughout Central and South America. No subspecies are currently recognised. However, herpetologists and reptile collectors have pointed out strong physical differences between some of the island populations of Iguana iguana and those from the continent. Drawing on both morphological and genetic data, this paper describes two subspecies of the Common green iguana Iguana iguana from the southern Lesser Antilles, specifically the countries of Saint Lucia Iguana iguana sanctaluciae and Iguana iguana insularis from St Vincent & the Grenadines, and Grenada. The form on the island of Saint Vincent has not been identified. The new subspecies are described based on the following unique combination of characters: Presence of high median and medium to small lateral horns on the snout; Small subtympanic plate not exceeding 20% of the eardrum size; Two or three scales of decreasing size anterior to the subtympanic plate; Fewer than ten small to medium triangular gular spikes; Medium sized dewlap; Low number of small to medium dispersed nuchal tubercles; Dark brown iris, with the white of the eye visible; Oval, prominent nostril; Short and relatively flat head; High dorsal spines; No swelling of the jowls in reproductively active males. Iguana iguana sanctaluciae has in adults vertical black stripes on body and tail and a black dewlap whereas Iguana iguana insularis is pale grey or creamy white in adults. Both subspecies are globally threatened by unsustainable hunting (including the pet trade) and by invasive alien species, including hybridization from invasive iguanas from South and Central America (I. iguana iguana and I. rhinolopha, considered here as full species) that have become established in all three countries. The authors call for stronger measures to conserve the remaining purebred Iguana i. insularis and Iguana i. sanctaluciae ssp. nov. throughout their ranges and for further research to identify other cryptic species and subspecies of Iguana in the Lesser Antilles.

The worldwide increase of hybridization in different groups is thought to have become more important with the loss of isolating barriers and the introduction of invasive species. This phenomenon could result in the extinction of endemic species. This study aims at investigating the hybridization dynamics between the endemic and threatened Lesser Antillean iguana (Iguana delicatissima) and the invasive common green iguana (Iguana iguana) in the Lesser Antilles, as well as assessing the impact of interspecific hybridization on the decline of I. delicatissima. 59 I. delicatissima (5 localities), 47 I. iguana (12 localities) and 27 hybrids (5 localities), who were all identified based on morphological characters, have been genotyped at 15 microsatellites markers. We also sequenced hybrids using ND4 mitochondrial loci to further investigate mitochondrial introgression. The genetic clustering of species and hybrid genetic assignment were performed using a comparative approach, through the implementation of a Discriminant Analysis of Principal Component (DAPC) based on statistics, as well as genetic clustering approaches based on the genetic models of several populations (Structure, NewHybrids and HIest), in order to get full characterization of hybridization patterns and introgression dynamics across the islands. The iguanas identified as hybrids in the wild, thanks to morphological analysis, were all genetically F1, F2, or backcrosses. A high proportion of individuals were also the result of a longer-term admixture. The absence of reproductive barriers between species leads to hybridization when species are in contact. Yet morphological and behavioral differences between species could explain why males I. iguana may dominate I. delicatissima, thus resulting in short-term species displacement and extinction by hybridization and recurrent introgression from I. iguana toward I. delicatissima. As a consequence, I. delicatissima gets eliminated through introgression, as observed in recent population history over several islands. These results have profound implications for species management of the endangered I. delicatissima and practical conservation recommendations are being discussed in the light of these findings.