BATS and AGAVES

Howard Scott Gentry (1903-1993) was a world authority on agaves. Gentry wrote, "Agaves are unique in the whole plant world, not merely because of their succulent character but because of a special role they have played in the indigenous civilizations in North America."

Some of these "unique" historic plants are pollinated and cross-fertilized by a unique animal of the mammal world, the bat.

The New York Botanic Gardens Plant/Bat Database shows that as of April 2005 researchers have established that 14 named species of agaves are pollinated by 5 species of bats.

There are approximately 200 to 300 species of agave plants in the southwestern US, Mexico, Central America, northern South America and the Caribbean Islands.

A tally of the New World Tropics bat species listed in Bats of the World shows that there are 38 species whose physical design is adapted for taking nectar from agave flowers. These bats have elongated muzzles and their long tongues are equipped with bristles. Another 34 species of bats include nectar in their diets.

It would appear that there are some 72 species of bats in the New World Tropics that are potential pollinators of between 200 to 300 species of agave plants. It is probably safe to say that further research will definitively establish that additional species of agave plants are pollinated by additional bat species.


A human being dwarfed by an agave rosette

Depending on the species, agaves grow from seed, root rhizomes or leaf axil bulblets. They produce a rosette of sword-like leaves close to the ground. Each leaf can be 2 to 3 metres long (6 to 9 feet). Under the skin of the leaves are many thread-like fibres. Some plant species have long strong fibres, other species have shorter, finer, weaker fibres.

Buried inside the rosette of leaves a big, solid, nutritious heart develops. After 8 to 20 years of life, the heart will send up a flowering stalk of 2 to 12 metres(1.5 feet to 4 feet). The plant then usually dies, but can live on through root rhizomes or bulblets or sprouting seeds.

Agaves are not the only plants that have this unique life style. The silversword of Hawaii, an Argyroxiphium species, exists as a rosette of leaves for 7 years. It is a member of the Compositae family and sends up a stalk clothed in brightly coloured daisy-like flowers.

Puya raimondii, the world's largest known Bromeliad, grows at 4000 metres (12,000 feet)in the Bolivian and Peruvian Andes. It lives as a rosette for 80 to 100 years, erects a 10 metre (9.5 foot)flowering stalk. A California specimen planted from seed flowered in 28 years, responsive perhaps to a milder climate and more generous amounts of water.

THE AGAVE-HUMAN CONNECTION, PLEASE.

We know that middle-American Indians had agave in their diets at least 9000 years ago. They probably ate agave pulp from the base of the leaves, from the plant heart and the flowering stalk.

HOW CAN YOU POSSIBLY KNOW WHAT A PERSON HAD TO EAT 9000 YEARS AGO?

By examining and carbon-dating mummified human feces and spat out agave fibres.

I AM TAKEN ABACK. IS THIS TOPIC APPROPRIATE FOR US TO DISCUSS?

We are discussing the results of top-drawer scientific methodology. For example, it is a current practice to examine the droppings of bats to find out what species of insects and fruit they have eaten. Researchers can identify plant species from the pollen grains in bat droppings. What works for one animal works for another.

In this particular case the procedure of examining archaeological finds of feces and spat out fibre identifies not only the food type but when it was eaten and where. The resulting information is historic and invaluable.

ALL RIGHT. WAS THE AGAVE PLANT JUST A SOURCE OF FOOD FOR THESE ANCIENT PEOPLE?

No. Bernal Diaz was a soldier in the army led by Cortez that visited what is now Mexico City in 1519. Diaz wrote a detailed account of that journey. He did not mention seeing the agave plant in the wild, but he wrote that sisal, a fibre from agave leaves, was used to make cloth for robes and to make sandals and that sisal cloth was used like paper for painting pictures of people and to outline maps.

Envoys from Montezuma painted pictures of some of the Spanish invaders and carried these paintings back to Montezuma. When the Spanish troops under Cortez needed guidance for further explorations, Montezuma provided them with maps of the east coast of Middle America and its rivers drawn on sisal fabric.

After the conquistadors under Cortez reached what is now Mexico City, they visited an outdoor market. Diaz wrote a vivid description of that vast, well-organized market replete with an amazing inventory of consumer goods. Among the precious metals, slaves, feathers, cloaks, cotton goods, chocolate, skins of animals, vegetables, herbs, live fowls and birds, pottery and timber were "those who sold sisal cloth and ropes and the sandals they wear on their feet, which are made from the same plant."

Travellers, archaeologists and anthropologists observed what the Indians were using sisal fibres for in the late 1800's and early 1900's. We can assume that those uses are historic. Some of the uses were:


A human being dwarfed by an agave plant in flower

The tall flowering shaft was used for:

Some leaf uses were and are:

Flower and root sap used to treat rattlesnake bites.

Agaves were/are planted to make hedges, living fences and as ornamentals.

When the Indians met the Spanish invaders they also met horses, burros and mules for the first time. Sisal fibres began to be used for horse tack including:

Sisal fibres began to be used to make webbing for European-style chairs and beds that the Spanish invaders preferred.

THIS SOUNDS LIKE A VALUABLE FIBRE. SURELY ITS USE PERSISTS TODAY.

Sisal fibres were very important in world commerce for some years. The sisal-producing agaves were carried to other countries and sisal production boomed. It was used for rope and most importantly for bailing twine.


Sisal drying racks

Around 1970 polythene products came on the market and agave leaves became much less important as a source of fibre for bailing twine and rope. This change in demand for agave leaf fibres has meant hardship for low income families in the sisal producing areas; Brazil, east Africa, Mexico, China and other parts of South America.

Efforts continue to rehabilitate sisal as a money-making commodity. It is used to make:

Agave leaf fibres can also be combined with polythene to make:

However, none of these many and innovative uses for sisal fibres has yet made up for the great demand that used to exist when sisal twine was used to tie bales of hay.

A visit to the Food and Agriculture Organization-United Nations website and a search for "sisal" will present thousands of website pages having to do with the sisal industry. A Tanzania project in 2005 was created to investigate the use of sisal waste to produce biogas as a source of electricity and energy production and as a biofertilizer. Also in 2005 a project was promoted in Brazil to replace asbestos with sisal in cement composites for building.

Gordon Mackie, an International Textile Consultant, has suggested that given the skyrocketing sales of agave-based mescal and tequila, some thought should be given to production of those alcoholic liquors from the hearts of the sisal agave species, mainly Agave sisilana, Agave fourcroydes and Agave amaniensis.

Mexican long-tongued bat, agave pollinator

There is a curious footnote to this discussion of sisal producing agave plants. Gentry says that the two main sources of commercial sisal, Agave sisilana and Agave fourcroydes, appear to be sterile. They do not produce seeds. Apparently their reproduction is solely by bulblets or root rhizomes. Even though bats are known to pollinate the flowers of those agave species, that practice apparently only benefits the bats.

There are a number of other agave species that are historic sources of long, strong fibres. Those agave plants set seed, are candidates for bat pollination and would be genetic banks for monoculture revitalization should disease strike the agave-sisal plantations.

The peril of monoculture destruction is not as threatening for the sisal industry as it is for the tequila industry. There is not the demand for sisal that there is for tequila. Sisal-agave plantations are in different parts of the world. A monoculture disease is unlikely to affect fields in all those locations. Tequila-agave fields are located only in two areas of Mexico and the industry is much more likely to be adversely affected by crop disease.

WHICH BRINGS US TO DRINKS PROVIDED BY AGAVE PLANTS.

Pulque, a tightly controlled intoxicant in Aztec life, has a grisly association with the human sacrifices that were common in that culture. However, it was and is a nourishing drink containing amino acids and other valuable nutritional constituents. It was a important dietary addition for people whose daily diet was low in protein.

The agave sap which accumulates in the heart of the plant prior to flowering is the basis for pulque. When the heart of the plant begins to enlarge, the bud is destroyed and a hollow made into the heart. The surrounding tissues continue to accumulate plant juices which are siphoned off and fermented to make pulque.

To read more about pulque and to see photographs of each step in pulque creation, visit http://www.mexicolore.co.uk, click on Aztec Home Page, click on Aztec Life and select "Getting Drunk on Pulque".

To make the distilled liquors, tequila and mescal, the entire heart of the agave plant, actually known as the head or cabeza, is processed. The resulting liquid is distilled and bottled.


In earlier days, the traditional conveyance for delivering agave hearts or cabezas to the distillery

I AM QUITE CERTAIN THAT BATS ARE NOT NEEDED TO POLLINATE ALL THE AGAVE PLANTS IN CULTIVATED FIELDS.

You are right. The huge cultivated fields of tequila agaves are planted from the root offshoots of other agave plants. It takes about 8 years for the heart of a tequila producing agave plant to be ready for harvest.

The big monocultures of agave plants are always at risk. They can become infected by disease and die. That happened recently in the tequila producing agave fields in Mexico.

Tequila has become a very popular alcoholic drink. For the last 20 years the amount of tequila demanded by consumers has risen every year. Tequila production provides jobs for thousands of people in Mexico. Tequila also brings big money into Mexico. Tequila is one of the most expensive liquors on the shelf in British supermarkets.

With the big economic boom in the tequila industry came disaster. The monocultures were stricken by disease.

When monocultures die, growers may have to get a fresh start from wild plants. Bat pollination and cross-fertilization of wild plants helps to ensure that this genetic resource survives.

The tequila producing agave growers are also beginning to revise the monoculture growing patterns. This includes mixing other species of agaves among the tequila agaves, planting other crops, such as legumes, among the tequila agaves and allowing some agaves to reach full maturation with flowering stalks. If flowering takes place, bats should be flying in the commercial agave fields helping to ensure cross-pollination.

 

Lesser long-nosed bat pollinating an agave flower

 

References:

Altringham, John D., Bats; Biology and Behaviour, Oxford University Press, 1996

Arita, Hector T., Wilson, Don E., Long-Nosed Bats and Agaves: The Tequila Connection, BATS, Bat Conservation International, Volume 5, Number 4, December 1987.

Diaz, Bernal, The Conquest of New Spain, Penguin Books Ltd., 1963.

Fleming, Theodore H., Following the Nectar Trail, BATS, Bat Conservation International, Volume 9, No. 4, Winter 1991, Page 4.

Fujita, M.S. 1991. Flying Fox (Chiroptera:Pteropodidae) Pollination, Seed Dispersal, and Economic Importance: A Tabular Summary of Current Knowledge, Resource Publication No. 2, Bat Conservation International

Gentry, Howard Scott, Agaves of Continental North America, University of Arizona Press, 1999

Heywood, V.H., Editor, 1979. Flowering Plants of the World, Oxford University Press

King, John, Reaching for the Sun; How Plants Work, Cambridge University Press, 1997.

Mackie, Gordon, Overview of the Various Alternative Uses of Sisal; http://www.fao.org//docrep/004/y1873e/y1873e06.htm

New York Botanical Gardens Bat/Plant Databases http://www.nybg.org/botany/tlobova/mori/batsplants/database/dbase_main.htm

Nowak, Ronald M., Walker's Bats of the World, The Johns Hopkins University Press, 1994

Valenzuela-Zapata, Ana G., Nabhan, Gary Paul, Tequila: A Natural and Cultural History, University of Arizona Press, 2004.


 

 

THE PLANT

Agave

  • Order: Liliales
  • Family: Agavaceae (Sisal Hemp, Pulque and Dragon Tree)
  • Genus: Agave
  • Species: About 300 species

THE BATS

  • Lesser long-nosed bat (Leptonycteris curasoae)
  • Mexican long-nosed bat (Leptonycteris nivalis)
  • Cuban flower bat (Phyllonycteris poeyi)
  • Long-tongued nectar bat (Glossophaga soricina)
  • Mexican long-tongued bat (Choeronycteris mexicana)
  • Seychelles flying fox (Pteropus seychellensis)
  • Marianas flying fox (Pteropus mariannus)

 

Fujita, M.S. 1991. Flying Fox (Chiroptera:Pteropodidae) Pollination, Seed Dispersal, and Economic Importance: A Tabular Summary of Current Knowledge, Resource Publication No. 2, Bat Conservation International

New York Botanical Gardens Bat/Plant Databases http://www.nybg.org/botany/tlobova/mori/batsplants/database/dbase_main.htm

Text and illustrations by Mary Louise Alley-Crosby who thanks Dr. Merlin D. Tuttle, Founder and President of Bat Conservation International, Austin, Texas, for permission to use his photographs of the lesser long-nosed bat as source material.

April 2006