The Crocodile Farm

According to the Ramsar Convention*, Bahía Tenacatita is one of the five most important bays on the Pacific Coast of Mexico. Estero La Manzanilla, an estuary on the east side of the bay, supports a mangrove forest in good condition. It is one of three estuaries on the coast with a large population of American crocodiles. During our stay in La Manzanilla, we often walked down a dirt road by the estuary to the restaurants on the beach. A sign said the area was a crocodile farm (cocodrilario) and a sagging chain-link fence was all that separated pedestrians from large crocodiles basking in the sunshine.

Be careful. Crocodiles in this area. Do not swim. Do not feed the crocodiles. Do not walk your pets. Do not fish. 

Ejido (land cooperative) La Manzanilla is known as el pueblo de los cocodrilos (the village of the crocodiles) and ejidatarios (members of the cooperative) are called to return individuals that stray from the estuary. The idea for the crocodile farm was born after the 1995 Colima earthquake and tsunami caused so much damage to La Manzanilla (link). The government of Jalisco and the Jesuit University of Guadalajara came up with the idea of ecotourism to help the people of La Manzanilla economically and psychologically. But it wasn't until the drought of 2001-2002 dried three-quarters of the estuary killing a number of crocodiles that the government began to provide the funds for the project (link). 

American crocodile (cocodrilo americano)

We took a tour of the estuary with Dave Collins, the owner of Immersion Adventures, who has spent a decade in the area as an Earthwatch coordinator, ecotourism guide and conservationist (link). Six gringos climbed into a paddle-powered, fiberglass panga with Dave and his boatman and headed out into the estuary.

American crocodiles in the lagoon

While systematic ecological studies are lacking, Estero La Manzanilla is presumed to be an important ecosystem from the presence of a large variety of fishes and reptiles that use it for feeding and reproduction, and as a nursery for their young. The mangrove forest produces a lot of leaves and detritus forming the base of extensive food webs and is habitat for a wide variety of resident and migrating birds. [Unless otherwise noted, information about Estero La Manzanilla comes from the Ficha Informativa de los Humedales de Ramsar (Information Record of Ramsar Wetlands, Site no. 1789, listed in 2007; link).

Water trail through the estuary

The brackish estuary is 6.5 km long roughly paralleling the coast; there are 54.6 ha (135 ac) of water and 200 ha (495 ac) of mangroves. The estuary is only connected to the ocean during the summer rainy season (700-800 mm/yr; 28-32 in/yr) when freshwater inflow from the Río Purificación breaks through the sand dunes. Dave said that the estuary was 12-19 ppt (parts per thousand salinity; the Pacific Ocean is about 35 ppt) and that the yellow mangrove leaves we saw on the surface were dropped by the trees after they fill up with salt. [See this link for more about Dave Collins (link).]

Tourist pangas in the estuary

Four species of mangroves occur in Estero La Manzanilla. The white mangrove (mangle blanco), which Dave said was the most abundant, and the buttonwood (botoncillo) occur near the beach while the red mangrove (mangle rojo) and black (mangle negro) occur in the interior. The 200 ha of mangroves is approximately 9% of total mangroves in the state of Jalisco and 3% of the total mangroves in the Central Pacific of Mexico.

Mangroves

The American crocodile (cocodrillo americano) is a symbol of La Manzanilla and a popular tourist attraction. The estuary supports about 300 individuals and is one of three principal crocodile populations along the coast of the state of Jalisco. [About 1000-2000 American crocodiles live in Mexico and Central and South America, but population data are incomplete (link).] Because of its abundance and biomass, as well as its predatory role in regulating the dynamics of the ecosystem, the crocodile is considered a key species of the estuary. Before the fence was installed, there was no barrier separating the crocodiles from the La Manzanilla; occasionally crocodiles captured a stray dog or cat that wandered too close (link).

American crocodiles and white ibis taking a bath

On the Pacific Coast, American crocodiles occur from southern Mexico through Central America to Venezuela and Peru in coastal areas and brackish river systems. They prefer salinity and have salt glands under their tongues. Mature males are generally 4.1-4.8 m long (13-16 ft) and weigh about 400 kg (880 lb); females rarely exceed 3.8 m (12 ft) (link).

American crocodile

Female American crocodiles create nests of sand, mud and vegetation, and lay 30-70 eggs in late winter-early spring (Dave said that local crocodiles placed their nests beneath white mangroves). The eggs incubate for 75-80 days while the parents guard the nest. The eggs hatch around the time of the first rains of summer (link). Estero La Manzanilla is critical to crocodile survival, especially during adverse climatic and hydrologic events, like the one that occurred in 2002 when the estuary experienced severe drying and some crocodiles were observed in a state of malnutrition and dehydration, and adult crocodiles were observed hiding in holes (encuevados). 

American crocodile

American crocodiles prey primarily on fishes (indicated by the narrow snout) throughout their lives, but their diet also includes, snails, crabs, turtles, birds and mammals (link). While the signs say "No alimentar a los cocodrilos" (Do not feed the crocodiles), some people toss fish carcasses over the fence. The fact that a commotion at the fence draws several crocodiles from a distance shows that they're habituated to this practice. 

Crocodiles gather to feed on fish carcasses that people toss to them

Occasionally, crocodiles leave the estuary, cross the dunes and beach and head for the ocean to find food, or they swim down the channel cut through the dunes during the summer rainy season. Crocodiles in shallow coastal waters creates issues for beach goers and fishermen are called into to capture and return them to the estuary (link, link).

Capturing a crocodile on the beach at La Manzanilla (photo from: link)

Fifty-five species of aquatic birds have been identified in Estero La Manzanilla, which is about half of all the aquatic bird species identified along the Jalisco coast. Twenty-one species of resident aquatic birds reproduce in the mangroves, including the boat-billed heron and the anhinga. The estuary has the largest breeding colony of boat-billed herons (garza cucharón) along the Jalisco coast.

Boat-billed Heron in the mangroves

Boat-billed Heron on a nest in the mangroves

Twenty-five species of migrating aquatic birds have been observed in the estuary. Herons and marine birds, including green herons and Neotropical cormorants, use estuarine habitats for feeding, roosting and raising their young.

Neotropical cormorants (top), great egret (center), great-tailed grackle (upper right), green iguana (behind egret) and hanging nest of a yellow-winged cacique

Green kingfisher

Great egret

Anhinga

The estuary supports a diverse array of fishes; 42 species occur in the lagoon and the mangroves representing about 80% of the ichthyofauna present in the largest estuarine-lagoon systems of Pacific Mexico. These species include mullets (lisas), mojarras, snappers (pargos), snooks (robalos), catfish (bagres) and sleeper gobies (chococos y guavinas).

Yellowfin mojarras (Gerreidae)

All of the species recorded in the lagoon have an ontogenetic relationship with estuarine systems, using estuarine and freshwaters during different life history stages for feeding, growth or reproduction, creating an ecological and biological interdependence between the coastal lagoons and marine waters. Fish like mullets produce thousands of larvae and juveniles in fall and winter in freshwater; in the estuary they convert detritus into biomass that is consumed by birds, reptiles, amphibians and fishes contributing to the stability of the system.

White mullets (Mullidae)

There are no estimates of the proportion of the population of La Manzanilla that directly use the goods and services (los bienes y servicios) provided by the estuary, but it must be significant. The urban developed zone extends onto the sandbar between the estuary and the ocean, and various organized groups (fishermen, tourist services, restaurants, walking vendors and others) use the area bordering the estuary for their economic activities.

Red mangroves

Estero La Manzanilla provides protection from saltwater inundation during hurricanes and flooding during periods of continuous rainfall. Excess water from the developed zone drains through arroyos and artificial canals into the estuary. The estuary also plays an important role in the regulation of the local aquifer, the community’s source of municipal water. Measurements of water quality in artesian wells indicated possible increasing salinization (link) due to the over exploitation and reduced rainy-season recharge due to deforestation in the surrounding hills.

Green iguanas 10 m (33 ft) off the ground [upper one is 1.5 m (5 ft) male with a dewlap]

Since 1970, urban growth and deforestation have had negative impacts on the estuary. A road constructed along the Jalisco coast (Mexico 200) in the 1970s limits freshwater flow into the estuary. In the 1980s, a paved access road into the beach at Boca de Iguanas divided the estuary into two parts limiting the freshwater flow between them. A dirt road built along the southwest margin to provide access to the dunes and the beach removed mangrove trees.

Mexico 200 north of La Manzanilla (flowering tree is a primavera)

Development around the estuary has potential to change the ecological characteristics of the estuary. Domestic waste and rubbish produced by the people living around the margin negatively affects the quality of the habitat. Deforestation of the hills around the estuary increases the amount of sediments reaching the lagoon during rain storms. Cutting of mangroves along the margin of the estuary next to the sand dunes reduces crocodile habitat.

Abandoned RV campground on the sand dunes between the beach and the estuary

*Formally known as the Convention on Wetlands of International Importance, Ramsar is an international treaty for the conservation and sustainable use of wetlands that recognizes their ecological functions and their economic, cultural, scientific and recreational value. It is named after the city of Ramsar, Iran where it was signed in 1971 (link).