San Diego Natural History Museum--Your Nature ConnectionSDNHM Biodiversity Research Center of the Californias
Agua Verde–Punta Mechudo Binational Expedition

Binational Expedition to Agua Verde and Punta MechudoDAY THIRTEEN
Monday, November 17, 2003

Ciudad Constitución to San Evaristo, Baja California Sur (Map locations 5,6,4)
Transmitted from camp by an Apple computer hooked to a Qualcomm/GlobalstarUSA satellite phone.

San Evaristo Base-Camp Up and Running

We left Ciudad Constitución early and made it to La Paz by 10:00am. We stopped in to the headquarters of Baja Expeditions to talk to Tim Means and to pick up the supplies he had purchased for us the day before. In order to save time, we had emailed him from Los Dolores using the satellite phone with a shopping list (food, batteries, drinks, etc.).

After packing up the trucks with crates of oranges and boxes of food, we headed north to San Evaristo. It was a four and a half hour drive to our new base-camp. The road showed plenty of signs of hurricane damage with plenty of washed-out sections. When we arrived at the new base-camp, Carolina already had the full kitchen up and running. She was certainly happy to see all the fresh produce.

Team Mammals and Team Birds were in full swing and I should be able to give you updates on their activities as soon as possible. In the meantime, Dr. Mike White from the Conservation Biology Institute has been working on the materials he collected during the first phase of the expedition from Los Dolores. He is a limnologist, but I’ll let his update explain the details of this field of science.

Team Limnology Update
Observations of Aquatic Systems in the Misión Dolores Region of the Agua Verde/Cerro Mechudo Corridor
Limnology is the study of inland bodies of water, such as lakes and rivers. Limnological investigations within the corridor are being led by Dr. Michael White, and are focused on developing a basic understanding of the hydrology, chemistry, and biology of the aquatic systems present in the area. In the area around the Misión Dolores base-camp, there are three general categories of aquatic systems: streams, lakes, and coastal lagoons. Streams that have been explored in the Misión Dolores region include the Arroyo Dolores (which holds the ruins of the historic Misión Dolores), the Arroyo San Clemente (a tributary to Arroyo Dolores), and the Arroyo La Cumbre (located in the canyon south of the Arroyo Dolores).

These stream systems have been greatly affected by the hurricanes (chubascos) that passed over the region in the summer. The tremendous amount of water that they dropped in the local watersheds was apparent from the minimal amount of vegetation remaining in the stream channels, the large deposits of vegetation debris (often several meters up in the remaining trees), and evidence of extensive reworking of the stream channels, which entailed moving large volumes of boulders and cobble stones.

The influence of the chubascos was also apparent in the amount of freshwater present in the arroyos. Flowing water is associated with warm mineral springs in both the Arroyo Dolores and the Arroyo La Cumbre. The Arroyo Dolores is particularly notable for the amount of freshwater it discharges, which is why the site proved to be suitable for establishing the Misión Dolores. Water was brought to the mission from a spring emerging from the canyon wall in the upper portion of the arroyo to a cistern (pila) via an aqueduct (acequia), which are still visible today. At the spring that supplied the old Misión and existing rancho (and the Expedition base-camp), we recorded the water temperature at 31ºC and conductivity of 730µS. Conductivity is a measure of the dissolved mineral content of the water. At the large spring in the Arroyo La Cumbre, which supplies water to about a dozen families living in the canyon, we recorded the water temperature of 32ºC and conductivity790µS.

To look more closely at the variation in water chemistry in the Arroyo Dolores, Dr. White and Bob Hill took measurements of temperature and conductivity at a number of locations within the Misión Dolores. Within this arroyo, there are sections of the stream where water was flowing on the surface, sections where it was present in isolated ponds, and reaches where surface water was absent but present in the underground aquifer. The conductivity of surface water appeared to increase as one moved higher up the arroyo. Conductivity ranged from 920µS at the bottom of the arroyo to in excess of 1990µS at the uppermost pool we visited.

Organisms that rely on aquatic systems in arid environments such as the Misión Dolores region, must cope with large fluctuations in many factors such as the amount of water, velocity of flow, temperature, and chemistry. Maggie Reinbold, Carlos Flores, and Dr. White collected various invertebrate taxa such as mayfly larvae, beetles, dragonfly larvae, snails, and zooplankton. The organisms will be identified to increase our understanding of the biogeography and ecology of these species in Baja California Sur.

One of the most interesting aquatic system explored in the first phase of the Expedition was Laguna Kakiwi, located on a mesa south of the Arroyo La Cumbre. Laguna Kakiwi is a very large ephemeral (temporary) lake, which fills only with significant precipitation events such as those associated with chubascos. Our local guide told us that Laguna Kakiwi had not held water for 15 years, and takes 2-3 years to completely dry.

Laguna Kakiwi had very turbid water, with extremely low transparency. The turbidity was probably associated with clay particles suspended in the water column by wind blowing across the lake. The conductivity of the lake was very low (140µS). By comparison, the conductivity of drinking water in the San Diego area is often over 500µS.

The limnology team also collected invertebrates at Laguna Kakiwi. A very interesting find was an Anostracan crustacean (fairy shrimp) in the genus Streptocephalus (fairy shrimp in this genus also occur in San Diego County). These and other aquatic animals that live in ephemeral lakes have life history strategies that allow them to survive periods without water, which in the case of Laguna Kakiwi can be for very long periods of time. These organisms develop resting stages (e.g., eggs and cysts) that can remain viable in the dry sediments of the lake for many years. When the lake fills with rain, the organisms emerge to complete their life cyles, and produce resting stages for future dry periods. The ephemeral Laguna Kakiwi is very unique in many respects. For example, the botany team found a very unique plant community around the margin of the lake that is associated with the ephemeral water conditions.

Along the beach, adjacent to our base-camp, there are 4 coastal lagoons. These lagoons vary in their salinity, reflecting the influences of tidal exchange and freshwater inflows. The lagoon at the terminus of the Arroyo Dolores is completely separated from the ocean by a sand bar. The salinity of the lagoon is 4 parts per thousand (ppt), reflecting the input of freshwater via groundwater. Two of the lagoons have daily tidal exchange with the ocean, and their salinities range from 33-36 ppt. There is also an interesting pond situated in a topographic depression that is separated from the ocean by a sand dune. The pond is used by the people living in the area to make salt. The deeper portions of the pond (which have been excavated for the salt making process) exhibited an interesting vertical layering of its water with denser brine (>100 ppt) on the bottom and less dense saline water (21 ppt) on top.

Bradford Hollingsworth
Expedition Coordinator
Mike White with Limnology Update
From San Evaristo base-camp at 11:00pm

Driving north along the road to San Evaristo.
Driving north along the road to San Evaristo.

Remnants of hurricane damage.
Remnants of hurricane damage.

San Evaristo
San Evaristo.

Dr. Mike White from the Conservation Biology Institute
Dr. Mike White from the Conservation Biology Institute.

Freshwater shrimp caught at Lago Kakiwi on November 10th.
Freshwater shrimp caught at Lago Kakiwi on November 10th.

Tuesday, November 18, 2003

San Evaristo, Baja California Sur (Map location 4)
Transmitted from camp by an Apple computer hooked to a Qualcomm/GlobalstarUSA satellite phone.

Team Bird and Team Mammal Start Their Work
Dr. Sergio Ticul Alvarez Castañeda examines mammal specimen. Photo by Dr. Monica Monica Riojas
Dr. Sergio Ticul Alvarez Castañeda examines mammal specimen.
Photo by Dr. Monica Riojas.

Little Desert Pocket Mouse (Chaetodipus arenarius)
Little Desert Pocket Mouse (Chaetodipus arenarius).

Phil Unitt and Edith Suazo  setting a mist net.
Phil Unitt and Edith Suazo setting a mist net.

Chestnut-sided Warbler (Dendroica pensylvanica)
Chestnut-sided Warbler (Dendroica pensylvanica).

Phil Unitt with Milan Mitrovich and Dr. Mónica Riojas
Phil Unitt with Milan Mitrovich and Dr. Mónica Riojas.

The two new teams studying birds and mammals have been working for two full days now. Both have been setting live-traps and mist nets. They are selectively sampling for new records for the region. As their updates report, they are already having great success! In the meantime, members of Team Herp and Team Botany (plus Limnology and Mycology) hiked towards Ojo de Venado; a lake similar to Lago Kakiwi but located further to the south (Ojo de Venado is located at N24°56’W110°45’). Using a local guide, they were able to reach the lake and again sample the freshwater shrimp, take water samples, and analyze the annual plant community.

Team Mammal Update
Hampered by horrible road conditions, two flat tires, and one stuck van, Team Mammal arrived in San Evaristo a bit later than anticipated on November 16, accompanied by Team Bird and some herpetological reinforcements. We lost no time getting to work documenting birds and mammals in this new wonderland. Dr. Wayne Spencer, Dr. Eric Mellink, Scott Tremor, Dr. Mónica Riojas, and Dr. Sergio Ticul Álvarez set several traplines for small mammals, with assistance from enthusiastic Mexican students and American biologists. We’ve so far sampled sand dunes and desert slopes and washes within a few kilometers of camp, and have captured numerous specimens of unique Baja endemics, including local subspecies of spiny pocket mice, little desert pocket mice, desert woodrats, antelope squirrels, and Eva’s desert mouse. After checking traps each morning, Scott and others prepare museum specimens while Wayne goes searching for specimens and collecting them with the use of a pellet gun to collect some less trap-happy species, like squirrels and rabbits. His pellet gun and Eric’s shotgun have also supplemented the bird collection for species not easily captured in the mist nets set by Team Bird, like roadrunners and Gila woodpeckers. At night, some members mist net for bats, while others spotlight for nocturnal species.

One general impression is that many mammal species here are dark and richly colored compared with those in other desert regions. The coyotes, antelope squirrels, and jackrabbits are strikingly colored, beautiful animals. At least one species we’ve captured represents a significant range extension for its kind: the little desert pocket mouse (Chaetodipus arenarius) has been previously recorded west of the mountains and in sand dunes near La Paz, but was a surprise in this geographically isolated pocket of dunes east of the mountains. The significant population we’ve documented here may well represent a new subspecies, but confirming this will require careful comparative analysis back at the museum.

The students are benefiting greatly from interaction with the more experienced participants and gaining experience with the realities and techniques of field work. The more experienced participants are also benefiting from the enthusiasm, fresh ideas, and hard work of the students.

Team Bird Update
Phil Unitt, Rob Hamilton, Ian McGregor, and Edith Suazo have been using a nearby canyon called El Bosque to mist net. Rob, Ian, and Edith run the nets, while Phil works on preparing specimens throughout the day. This crew has hardly shown themselves around base-camp, other than to come in for dinner and some sleep. Rob has promised me a detailed update for tomorrow's update, but wanted to share their most exciting find right away. Yesterday, they were able to capture the first specimen of the Chestnut-sided Warbler (Dendroica pensylvanica). Up until now, this species has only been observed visually on the peninsula. It is not known whether this specimen was still in migration, or whether it is over-wintering here. The specimen had a moderate amount of fat, which leaves it ambiguous. If it had a large amount of fat, this would indicate that it was in migration. There is certainly more to come from Team Bird; they appear to be just getting started.

Bradford Hollingsworth
Expedition Coordinator
Wayne Spencer from the Conservation Biology Institute with Team Mammal
Phil Unitt, from Team Bird, being asked questions as he continues to prep specimens.
From San Evaristo base-camp at 11:00pm

Day Fourteen photos by Wayne Spencer. Other photos by Bradford Hollingsworth


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Agua Verde-Punta Mechudo Expedition | Binational Multidisciplinary Expeditions | BRCC