Conservation of Antillean manatees in the Drowned Cayes area of Belize

The purpose of this study was to determine how manatees use Swallow Caye, Drowned Cayes, and Gallows Reef, three distinct habitat types within the Belize Barrier Reef lagoon system near Belize City. Data were collected using boat-based point scan methods with the assistance of volunteers. Presence/absence and photo ID methods ensured consistency of data collection despite a changing pool of volunteer researchers. Results confirmed the mangrove and seagrass ecosystem between the Belize Barrier Reef and Belize City as important manatee habitat. Inconsistent with the prevailing "seasonal distribution hypothesis" for manatees in Belize, the probability of encountering manatees at Swallow Caye and in the Drowned Cayes was equal between dry and wet seasons. However, manatees were only observed at Gallows Reef during the wet season. Swallow Caye had the highest probability of encountering manatees, confirming traditional knowledge held by local tour operators, which led to the establishment of Swallow Caye Wildlife Sanctuary in 2002. In contrast to previous studies, my data suggest that at least 44% of the manatee population carry scars from non-lethal boat strikes. The proportion of scarred animals did not vary as a function of habitat type, season, or year. The probability of encountering manatees did not change between years, despite an exponential increase in cruise ship tourism. Marine Protected Areas (MPAs) and wildlife protection laws indicate that Belize is working to meet obligations under international agreements. However, there is still cause for concern. Manatees do not remain inside designated refuge boundaries; governmental agencies depend on co-management agreements with local non-governmental organizations for enforcement of rules inside MPAs; regulations governing human behavior outside MPAs are lacking; funds for monitoring and evaluation of MPAs are lacking. Manatee conservation strategies should be integrated into a system of riverine, coastal, and marine protected areas supported by additional tactics such as required manatee training for boat captains, slow zones at hot spots outside MPAs, and continued educational outreach. With few modifications and increased enforcement and monitoring, the Belize model for manatee conservation could lead to a shared "triumph on the commons" for the manatees and the user groups that shared their habitat

The Magnitude of Global Marine Species Diversity

Background: The question of how many marine species exist is important because it provides a metric for how much we do and do not know about life in the oceans. We have compiled the first register of the marine species of the world and used this baseline to estimate how many more species, partitioned among all major eukaryotic groups, may be discovered. Results: There are ∼226,000 eukaryotic marine species described. More species were described in the past decade (∼20,000) than in any previous one. The number of authors describing new species has been increasing at a faster rate than the number of new species described in the past six decades. We report that there are ∼170,000 synonyms, that 58,000–72,000 species are collected but not yet described, and that 482,000–741,000 more species have yet to be sampled. Molecular methods may add tens of thousands of cryptic species. Thus, there may be 0.7–1.0 million marine species. Past rates of description of new species indicate there may be 0.5 ± 0.2 million marine species. On average 37% (median 31%) of species in over 100 recent field studies around the world might be new to science. Conclusions: Currently, between one-third and two-thirds of marine species may be undescribed, and previous estimates of there being well over one million marine species appear highly unlikely. More species than ever before are being described annually by an increasing number of authors. If the current trend continues, most species will be discovered this century

The status of the world's land and marine mammals: diversity, threat, and knowledge

Knowledge of mammalian diversity is still surprisingly disparate, both regionally and taxonomically. Here, we present a comprehensive assessment of the conservation status and distribution of the world's mammals. Data, compiled by 1700+ experts, cover all 5487 species, including marine mammals. Global macroecological patterns are very different for land and marine species but suggest common mechanisms driving diversity and endemism across systems. Compared with land species, threat levels are higher among marine mammals, driven by different processes (accidental mortality and pollution, rather than habitat loss), and are spatially distinct (peaking in northern oceans, rather than in Southeast Asia). Marine mammals are also disproportionately poorly known. These data are made freely available to support further scientific developments and conservation action

Changes in Bottlenose Dolphin (Tursiops truncatus) Distribution and Behavior in the Drowned Cayes, Belize, and Correlation to Human Impacts

Human activity can greatly influence the behavior and distribution of bottlenose dolphins (Tursiops truncatus). This project focused on the distribution and behavior of bottlenose dolphins in the Drowned Cayes, Belize. Prior to the 2000s, the area was relatively undeveloped and undisturbed and had minimal human activity. Since 2000, fish camps, small resorts, and cruise ship tourism have flourished in the area. This has caused an increase of over 800,000 visitors from 1998 to 2006. Boat-based survey data were collected from 2005 to 2015 and compared to results from surveys conducted in 1999-2000. Total dolphin observation time as a percentage of total survey time was 17.2% in the 1999-2000 dataset and 10.8% in the 2005-2015 datasets. This decrease in observation time suggests that the dolphin population in the Drowned Cayes has decreased since the late 1990s. However, these values could be influenced by survey methods. In 2015, cruise ship presence in the area was also recorded. Eighty-nine percent of the total observation time for 2015 occurred on days for which there were zero cruise ships present, suggesting that dolphins may be avoiding the area when cruise ships are present. Foraging was the most frequently observed behavior in both 1999-2000 and 2005 to 2015 suggesting that the Drowned Cayes is used as a foraging area. That said, the percent of foraging activity was significantly higher in 1999-2000 (86.3%) than in 2005 to 2015 (57.4%), having dropped by 28.9%. Interestingly, there was a 23.6% increase in traveling behavior between 1999-2000 (9.2%) and 2005 to 2015 (32.8%). These behavioral changes could potentially be linked to increased human activity or other unidentified factors. Examining observed changes in behavior increases knowledge of this species in the study area and can provide insight for improved local management of this small dolphin population

Diagnosing Domoic Acid Toxicosis in the California Sea Lion (Zalophus californianus) Using Behavioral Criteria: A Novel Approach

Domoic acid toxicosis in the California sea lion (Zalophus californianus) is difficult to diagnose using presence of toxin alone because the duration of domoic acid presence in blood and urine is generally less than 48 hr following exposure. Because domoic acid toxicosis is often suggested by presentation of behavioral abnormalities, we asked whether assessment of behavior might be useful for diagnostic purposes. We developed an ethogram to categorize behavioral data collected via continuous focal animal sampling. In total, 169 subjects were observed at a rehabilitation center. Sea lions with domoic acid toxicosis displayed head weaving (P \u3c 0.0001) and muscle fasciculations (P \u3c 0.01) significantly more often than animals in a comparison group. Dragging hind flippers and swift scanning were observed exclusively in animals from the domoic acid toxicosis group. The data show that behavioral diagnostic criteria can be effective in the diagnosis of domoic acid toxicosis in the California sea lion

Reported incidence of manatee mortality in lakes (L), rivers (R), and coast & estuaries (C&E).

<p>The main features are that: (a) the number of sighted manatee carcasses increases downstream the lakes (with a peak in the rivers); (b) sighting three manatee carcasses or more associates highly with the sighting of four live manatees or more; (c) on average, one manatee carcass is sighted in all habitat types; however, such sightings are more frequent in the lakes and, to a lesser extent, in the rivers; (d) the incidence of catches increases from the lakes to the rivers and then to the coast & estuaries.</p

Manatee sighting and occurrence patterns in lakes (L), rivers (R), and coast & estuaries (C&E)

<p>. Items concerned are: (a) the proportion of respondents doing the sighting; (b) the monthly number of live sightings; (c) the number of manatees per sighting; and (d) the percentage of perceived increasing/stable trend in manatee numbers. The error bars represent the 95% confidence intervals together with the corresponding sample sizes (shown at panel bottom). An asterisk indicates effects that are significantly different at probability level of 5% or less.</p

Reported incidence of manatee mortality in lakes (L), rivers (R), and coast & estuaries (C&E).

<p>The main features are that: (a) the number of sighted manatee carcasses increases downstream the lakes (with a peak in the rivers); (b) sighting three manatee carcasses or more associates highly with the sighting of four live manatees or more; (c) on average, one manatee carcass is sighted in all habitat types; however, such sightings are more frequent in the lakes and, to a lesser extent, in the rivers; (d) the incidence of catches increases from the lakes to the rivers and then to the coast & estuaries.</p

Map of the study area.

<p>Surveyed villages are displayed together with the manatee distribution; the two large circles indicate the reported manatee hotspots.</p