Saguaros:The Crowned Jewel of the

Sonoran Desert

Do Saguaros Grow Older on the East or West Side of the Tucson

Mountains?

Our Hypothesis

• Null: There is no correlation between the side of the mountain, east or west, and age.

• Alternative: Saguaros on the West side will generally live to be older because they are not exposed to as much sunlight than those on the East side.

Importance

• Humans moving farther into the desert.

• Loosing habitat.

• Conservation increasingly important.

• To know what areas or regions will be better to conserve.

Background Information

• Saguaro Cacti (cereus giganteus)

• Slow Growth

• Sprout at 75 years

• Mature at 100 + yrs

• Oldest, up to 200 yrs

– More than 5 Arms

• Shallow Root System

Objective:

To determine if the geographical location of a Saguaro cactus on a mountain has any effect on the

age reached.

Technique:

• Observed number of arms on each saguaro.– On East & West Side of Tucson Mountain.

• Hiked and Counted 500 cacti on each slope

• Compiled our results into data.

WEST SLOPE

Cacti Counting

EAST SLOPE

DATA

• WEST SLOPE• 0 Arms - 165• 1 Arm - 45• 2 Arms - 89• 3 Arms - 90• 4 Arms - 80

• EAST SLOPE• 0 Arms - 253• 1 Arm - 41• 2 Arms - 66• 3 Arms - 82• 4 Arms - 62

East Slope vs. West Slope

050

100150200250300

# Cacti

0 1 2 3 4+

# Arms

East

West

Calculations

• WEST SIDE• 0 Arms - 200

– 39.7%

• 1 or more Arms - 304– 60.3%

• EAST SIDE• 0 Arms - 253

– 50.2%

• 1 or more Arms - 251– 49.8%

Results

• Reject null Hypothesis

• Accept Alternative Hypothesis

• Grow older on West Side of Mountain

0%

20%

40%

60%

80%

100%

West East

Side of Mountain

% Ca

cti No Arms

Arms

Overview

• Reasons why we think Saguaros grow older on the West Side of Tucson Mountain.– Less Sunlight– Conserve Water Loss– Farther from City Population– Less Detrimental to Saguaros, from Smog,

Pollution, etc.

Attack of the killer Cacti