North-east Falklands (Malvinas) Right Whale Wintering Area IMMA

Criterion B: Distribution and Abundance

Sub-criterion B2: Aggregations

The IMMA supports a regionally important wintering aggregation of southern right whales (Eubalaena australis), which use the region as a mating, socialising and resting area (Weir and Stanworth 2020, Weir 2022, Cerchio et al. 2022). Systematic research of baleen whales in the Islands only commenced in 2017, providing the first indication of the winter presence of right whale aggregations in nearshore areas (Weir, 2017). Since then, full winter seasons of coastal boat surveys to target the species have been carried out during 2019, 2020 and 2022 to assess its ecology and occurrence in the region (Weir and Stanworth 2020, Weir 2022).

Right whales have been present throughout the austral winter months of June, July and August in all three of those years, supporting the occurrence of persistent seasonal aggregations. Depending on the year, the aggregations are present between mid-May and early September, and whale numbers usually peak during July (Weir 2022). However, both sightings and acoustic monitoring indicate that a regular occurrence within the IMMA can commence as early as March in some years (Weir 2022, Cerchio et al. 2022), and that inter-annual variation probably relates to the foraging locations and prey availability in the months preceding the reproductive season.

The boundaries of the IMMA reflect the winter nearshore distribution of right whales and are based on: (1) results from small boat survey effort carried out between Cape Pembroke and MacBride Head on the north-east coast of East Falkland between 2019 and; (2) telemetry movements of 10 animals that were satellite-tagged in July 2022; and (3) opportunistic sightings from shore, boats and aircraft. Boat surveys (and anecdotal records) support a very regular occurrence in Port William and around Cape Pembroke during some years (Weir and Stanworth 2020), a regular annual use of Berkeley Sound (also confirmed by acoustic monitoring: Cerchio et al. 2022), and a concentrated occurrence in the waters between Volunteer Point and MacBride Head (Weir 2022, Falklands Conservation unpublished data). Telemetry confirmed that the remote north coast of East Falkland is also heavily used by the species, with multiple individuals spending significant time in that area and confirming previous anecdotal reports of whale aggregations by aircraft pilots.

Genetic analysis of right whale samples collected in the IMMA during 2019 and 2020 has demonstrated their connectivity with animals sampled at the Valdés Peninsula in Argentina (Jackson et al. 2022), which is the major calving area for the species in the south-west Atlantic. This indicates that southern right whales present in the IMMA in winter are part of the wider south-west Atlantic population that undertakes seasonal migrations between calving and feeding areas. Currently, the calving grounds are well-documented while the foraging areas remain relatively poorly described, and the Islands therefore potentially represent an important geographic link between some areas used for important life cycle activities at either end of the migration route.

Right whale numbers in the Islands peak earlier in the winter (July and August: Weir 2021, 2022) then they do at the Valdés Peninsula (September and October: Rowntree et al. 2001), suggesting that the same animals can potentially move between the two areas within the same breeding season. Satellite telemetry carried out during July 2022 showed that 6 of 10 animals tagged in the IMMA subsequently continued on to the Valdés Peninsula after leaving the Islands (https://falklandsconservation.com/southern-right-whale-tracking/). This indicates that whales (likely including pregnant females preparing to calve) may use the IMMA as a temporary migratory stopover, while transiting across open ocean between foraging areas and the Valdés Peninsula. Depending on their age-sex class and reproductive cycles, animals may potentially stop to socialise and mate, before continuing their migration.

Photo-identification and satellite-tagging data indicate that some individual animals remain within the IMMA for (at least) two consecutive months during winter, which emphasises the importance of the area as a destination rather than solely transitory use (Weir 2022, Falklands Conservation unpublished data). Satellite-tracking data confirm that individuals move back and forth along the coast during their time within the area. Inter-annual photo-identification recaptures confirm that some of the same individuals return to the site annually, indicating long-term site fidelity to the wintering area. Acoustic work in Berkeley Sound revealed a continuous daily presence of vocalising southern right whales between (at least) late May and early September (Cerchio et al. 2022), and it is considered highly likely that this continuous presence occurs across the entire IMMA.

The total number of whales using this area is currently unknown. Photo-identification effort during small boat work has catalogued around 300 individuals between 2017 and 2021 (Weir 2022, Falklands Conservation unpublished data). However, that effort has been very limited in spatial extent and its temporal frequency was strongly confined by weather conditions; consequently, the true number of animals using the areas is likely to be considerably higher. Estimating abundance across the IMMA will be the focus of targeted aerial survey work in 2023.

Criterion C: Key Life Cycle Activities

Sub-criterion C1: Reproductive Areas

The underlying driver for the right whale wintering aggregations in the IMMA (see Criterion B2) appears to be social and reproductive behaviour. Feeding has not been conclusively documented within the IMMA during winter, and defecations are very rarely observed and only by animals engaged in surface-active behaviour and clearly not feeding (Weir, pers. obs.). The presence of surface-active groups is considered indicative of mating behaviour, and frequent observations have been recorded of mating amongst pairs and groups (Weir and Stanworth 2019, Weir 2022, Falklands Conservation unpublished data). Additionally, two years of acoustic monitoring in Berkeley Sound recorded numerous calls and gunshot song; the latter is considered to be a form of male reproductive advertisement (Cerchio et al. 2022). No neonate calves have been recorded to date in the IMMA or adjacent waters, and it is considered to currently comprise a mating-only breeding area. However, the presence of juveniles suggests that right whale occurrence in the site encompasses more than solely mating behaviour for reproductive purposes, potentially including social behaviour and rest.