Phoque moine d'Hawaï

Historical threats to Monk Seals were documented in (Ragen 1999) and (Ragen and Lavigne 1999). The most recent Recovery Plan (National Marine Fisheries Service 2007) updated the threats to the species and concluded that the most crucial threats in the NWHI at that time were: 1) food limitation that could be due to changes in oceanographic conditions, legacy impacts of fisheries, or competition with other predators; 2) entanglement in marine debris, largely fragments of net and line abandoned, lost, or discarded by North Pacific fisheries; 3) predation by sharks, especially on pre-weaned and recently weaned pups; and 4) intraspecific aggression by male seals. Loss of terrestrial habitat due to sea level rise resulting from global warming was first identified as an emerging threat in the NWHI by (Baker et al. 2006), but has recently become undeniably more concerning (Baker et al. 2020a). In the NWHI, most of the terrestrial habitat used by seals comprises low-lying sand islands. The historically most-used pupping habitat at French Frigate Shoals, has been almost entirely lost to inundation due to gradual erosion and destructive storm events (Baker et al. 2020a). This habitat loss has been associated with extraordinarily high mortality of young pups. Additional losses of terrestrial habitat due to sea-level rise will most likely reduce the carrying capacity of various NWHI populations or in some cases, may render significant portions of the species range inaccessible (Reynolds et al. 2012, Baker et al. 2020a).

Threats to Monk Seals in the MHI are quite distinct from those in the NWHI, and include: 1) intentional killing by humans, 2) fisheries interactions, primarily hookings and entanglements in gillnets; 3) transmission of diseases from terrestrial animals to the seals, with toxoplasmosis being a primary concern (Barbieri et al. 2016, Gobush et al. 2017, Harting et al. 2020, Robinson et al. 2023). In recent decades, as the monk seal population has grown in the MHI where seals are more exposed to anthropogenically-impacted landscapes and domestic animals, infection with Toxoplasma gondii (a parasite for which cats are the obligate hosts) has emerged as one of the primary health threats limiting recovery of Monk Seals (Barbieri et al. 2016, Harting et al. 2020, Robinson et al. 2023).

The Hawaiian Monk Seal has been listed as Endangered under the US Endangered Species Act since1976. That law contains a number of provisions to protect the seals and their critical habitat. They are also covered by a general prohibition of unpermitted taking by the US Marine Mammal Protection Act of 1973.

Virtually all of the land and waters in the NWHI is included in one or more protected areas (the Northwestern Hawaiian Islands State Marine Refuge, the Kure Atoll State Wildlife Refuge, the Hawaiian Islands National Wildlife Refuge, the Midway Atoll National Wildlife Refuge, the Northwestern Hawaiian Islands Coral Reef Ecosystem Reserve, and the Papahānaumokuākea Marine National Monument), where in situ human activities that could affect the seals or their habitats are either prohibited or strictly controlled.

The Hawaiian Monk Seal is the focus of one of the most proactive marine mammal recovery programs in the world (Lowry et al. 2011). Historically, the primary focus of the species’ recovery program was to increase survival of juvenile and adult female seals in the NWHI. Important recovery efforts have included: 1) removing marine debris from entangled seals 2) cleaning up marine debris and toxic chemicals in the seal’s habitats; 3) minimizing human activities that could disturb seals; 4) mitigating shark predation of young pups through pup translocations and shark removals; 5) removing and translocating adult males to mitigate mortality associated with male aggression towards juveniles and females; 6) rehabilitating and releasing malnourished young seals and conservation translocations designed to improve juvenile survival; and 7) regulating fisheries to reduce the likelihood of direct and indirect interactions. Conservation efforts have had substantial impacts with up to 30% of the current Monk Seal population being alive today due to mitigation efforts targeted towards individual seals over more than 30 years (Harting et al. 2014).

Monk Seal conservation translocations have been conducted with a variety of objectives, including reducing shark predation and conspecific male aggression, stopping human–seal interactions, and taking advantage of regional differences in demographic patterns to improve survival (Baker et al. 2011b, Norris et al. 2017, Baker et al. 2020b).

Steps have been taken to guard against disease outbreaks that could decimate the population. Background surveys conducted on Hawaiian Monk Seals showed that they remain naïve (no detectable antibodies) to potential virus threats including morbillivirus (Littnan et al. 2006), which has been associated with marine mammal mass mortality events worldwide, and that has been detected in other species in Hawaii (West et al. 2013). Efforts to monitor population health are ongoing and a morbillivirus vaccination program initiated in 2016 has succeeded in vaccinating a large proportion of the Hawaiian monk seal population (Baker et al. 2017, Robinson et al. 2018). Vaccine and treatment options for toxoplasmosis are currently lacking. Nevertheless, ailing seals diagnosed with toxoplasmosis are provided with intensive medical care. Stakeholder engagement and public information campaigns have been developed to address the source (i.e. domestic cats) of Toxoplasma on the terrestrial landscape.

In 2014, The Marine Mammal Center opened Ke Kai Ola, a privately funded and managed rehabilitation facility, was constructed to support recovery efforts. Seals from across the archipelago that are sick, injured, emaciated, or otherwise in need of rehabilitation are cared for at this Hawaiian Monk Seal hospital. Forty-eight seals were successfully rehabilitated and released during 2014 to 2022.

Considerable effort has been spent on the recovery program to develop strategies to maintain population growth in the MHI, while mitigating human-seal interactions (Lowry et al. 2011). The program is currently working on strategies to prevent unwanted seal behaviors including fisheries interactions and animals conditioned to interact with people. A significant component of this work includes community engagement on how to avoid negative wildlife interactions.