The elaborate tail feathers of peacocks and impressive antlers of male deer have long fascinated those with an interest in animals. How could these traits evolve? Why are they dimorphic (usually only seen in the males of the species)? While the antlers could plausibly be an adaptation to thwart predators, surely this isn’t the case for the peacock’s tail feathers? The answer, it seems, lies in how individuals acquire mates. Females, by definition, produce few gametes (germ cells), but invest a relatively large amount of resources in each one. By contrast, males invest relatively little in individual gametes, but produce them in vast quantities. As a result, females (or more accurately their gametes) are limited, relative to males', and typically (although not always) males compete for reproductive access to females. It is now believed that the peacock's ornate tail serves to attract mates and the deer's antlers are used in physical combat among males for access to females. While these arguments (collectively termed 'sexual selection') have provided credible explanations for the evolution of these exaggerated traits, in some cases we are now faced with the complete opposite quandary. Specifically, why aren’t some animals, like the red squirrel, visually dimorphic? Put another way, if reproductive female red squirrels are a limited commodity, what traits are used by males to compete for access to them? Red squirrel males are only marginally larger than females, and don't possess either sexual weaponry like antlers, or ornamentation, suggesting that neither physical combat among males, nor visual attraction are important. At Kluane we are currently testing the hypothesis that the analogous trait to antlers and tail feathers in red squirrels is male behaviour. Because females defend individual territories, they are spatially scattered and males must search for reproductive opportunity. Could it be that the spatial abilities of male red squirrels represent their 'antlers'? To test this we following the males during the mating season to quantify their spatial behaviour and comparing their relative success, as the number of offspring that they sire. Should our hypothesis be supported, it could open the door to investigations of a far richer set of traits involved in sexual selection than has previously been appreciated.
It is hard work for animals to obtain food from the environment. They must move quickly to capture their prey or travel long distances to find suitable plants to eat. It is also a lot of work for animals to digest the food they obtain and then allocate food nutrients to maintaining their own health. The total amount of work an animal does per day is termed its daily energy expenditure. Scientists are interested in measuring the daily energy expenditure of animals in their natural environments. To do this, researchers use the fact that animals breathe in oxygen (O2) and breathe out carbon dioxide (CO2) and water (H2O). Similar to the last time that you ran up a couple of flights of stairs, when animals work hard, they breathe in more O2 and breathe out more CO2 and H2O. The technique uses special non-toxic water that is injected into animals. It estimates daily energy expenditure by measuring the amount of CO2 animals breathe out over a multi-day period. Regular water is composed of a ratio of two hydrogen atoms (H) to one oxygen atom (O) to make H2O. In the special water used in this procedure, the ratio between H and O is the same, but a proportion of the O and H atoms are naturally labelled O* and H*. For the technique, the special water is injected into the animal. The O* and H* molecules naturally mix with the other O and H atoms in the body water. A blood sample is collected to determine the initial concentration of O* and H*. Animals are released after the initial blood sample and behave normally for about two days. As they are busy working over this time interval they breathe out O* atoms in both CO*2 and H2O*, whereas the H* atoms are only breathed out through H*2O. The animal is then recaptured and another blood sample is collected. Scientists are able to quantify the amount of CO2 expelled, and thus get a measure of how hard the animal worked by comparing the ratio of O* and H* in a final blood sample to that in the initial blood sample. If the animals worked hard and expelled a lot of CO2 there will be a greater difference in the concentration of O* and H* between the initial and final blood sample. The amount of CO2 expelled can then be converted into an estimate of the daily energy expenditure of that animal.
-QF
-QF
Radio Telemetry
Definition
Telemetry (tele = distance, metry = measurement) refers to measuring from a distance. "Radio" telemetry refers specifically to telemetry in which information is transmitted over VHF radio waves. Although several aspects of an animal's biology can be measured remotely with telemetry, we use this tool specifically to measure a squirrel's position in space.
Components
There are three components to a radio telemetry system.:
1. A transmitter is worn by the animal subject. It transmits a pulsed signal (every 1.5 seconds) as a VHF radio wave. Squirrel transmitters weigh 4 grams and are worn around the neck.
2. A receiver receives the radio signal and translates it into something we can interpret such as an audible beep. The receiver can be tuned to receive specific radio frequencies within a broad range, thus one receiver can be used to identify and track multiple animals whose radio collars transmit at different frequencies.
3. An antenna amplifies the radio signal being received. A "directional" antenna receives the radio signal with different sensitivity (gain) depending on the orientation of the antenna - the beep is loud when the antenna pointed toward the animal, but becomes increasingly softer as the antenna turns away from the animal.
Techniques
In Squirrel Camp, we use radio telemetry primarily for radio tracking - following the radio signal until the animal is located visually. Starting at some distance from the squirrel, we travel in the direction in which the radio signal is strongest. As we get closer to the squirrel, the radio signal increases in strength, i.e. the beep gets louder, and we can reduce the sensitivity (gain) on the receiver for better sound resolution. We home in on the squirrel until we make visual contact. This gives us the squirrel's exact location in space, and allows us to observe its behavior at the time. Experienced researchers can locate squirrels in less than ten minutes with this technique.
Occasionally, we use triangulation to locate squirrels from a greater distance. Triangulation involves recording the direction from the observer to the squirrel as a compass bearing from two or more observer locations. These bearings are then plotted as lines on a map, which intersect at the animal's location. Unlike radio tracking which gives an exact location, triangulation involves some estimation error, but can be kept small by experienced researchers.
On foot in the boreal forest, we can detect the radio signals from squirrel radio collars from distances of about 300 meters. Antennas positioned higher can receive signals from greater distances. Common tactics to increase the range involve gaining elevation, and include climbing hills and trees, or when these are not available, standing on your vehicle.
Applications
Radio telemetry has many applications in wildlife biology. Telemetry-based analyses we conduct on the red squirrel project include:
Resource use - nest sites, feeding locations
Habitat selection - used sites chosen from among those available for use
Survival - Longevity, location and cause of death
Movement patterns - sequential locations of moving animals such as dispersing juveniles
Activity patterns - timing and duration of activity and sleep, nest use
Behavioral observation - focal sampling for determining diet, mating choices, caching behavior
Home range analysis - drawing polygons around a large set of mapped locations
-MCA
Definition
Telemetry (tele = distance, metry = measurement) refers to measuring from a distance. "Radio" telemetry refers specifically to telemetry in which information is transmitted over VHF radio waves. Although several aspects of an animal's biology can be measured remotely with telemetry, we use this tool specifically to measure a squirrel's position in space.
Components
There are three components to a radio telemetry system.:
1. A transmitter is worn by the animal subject. It transmits a pulsed signal (every 1.5 seconds) as a VHF radio wave. Squirrel transmitters weigh 4 grams and are worn around the neck.
2. A receiver receives the radio signal and translates it into something we can interpret such as an audible beep. The receiver can be tuned to receive specific radio frequencies within a broad range, thus one receiver can be used to identify and track multiple animals whose radio collars transmit at different frequencies.
3. An antenna amplifies the radio signal being received. A "directional" antenna receives the radio signal with different sensitivity (gain) depending on the orientation of the antenna - the beep is loud when the antenna pointed toward the animal, but becomes increasingly softer as the antenna turns away from the animal.
Techniques
In Squirrel Camp, we use radio telemetry primarily for radio tracking - following the radio signal until the animal is located visually. Starting at some distance from the squirrel, we travel in the direction in which the radio signal is strongest. As we get closer to the squirrel, the radio signal increases in strength, i.e. the beep gets louder, and we can reduce the sensitivity (gain) on the receiver for better sound resolution. We home in on the squirrel until we make visual contact. This gives us the squirrel's exact location in space, and allows us to observe its behavior at the time. Experienced researchers can locate squirrels in less than ten minutes with this technique.
Occasionally, we use triangulation to locate squirrels from a greater distance. Triangulation involves recording the direction from the observer to the squirrel as a compass bearing from two or more observer locations. These bearings are then plotted as lines on a map, which intersect at the animal's location. Unlike radio tracking which gives an exact location, triangulation involves some estimation error, but can be kept small by experienced researchers.
On foot in the boreal forest, we can detect the radio signals from squirrel radio collars from distances of about 300 meters. Antennas positioned higher can receive signals from greater distances. Common tactics to increase the range involve gaining elevation, and include climbing hills and trees, or when these are not available, standing on your vehicle.
Applications
Radio telemetry has many applications in wildlife biology. Telemetry-based analyses we conduct on the red squirrel project include:
Resource use - nest sites, feeding locations
Habitat selection - used sites chosen from among those available for use
Survival - Longevity, location and cause of death
Movement patterns - sequential locations of moving animals such as dispersing juveniles
Activity patterns - timing and duration of activity and sleep, nest use
Behavioral observation - focal sampling for determining diet, mating choices, caching behavior
Home range analysis - drawing polygons around a large set of mapped locations
-MCA
Part of what we are studying with the red squirrels is how their survival and reproduction is affected by how much food they have access to (you can read more about this on our project page). We are experimentally testing some of our hypotheses by giving some squirrels access to supplemental food - peanut butter! Peanut butter might seem like a strange thing to be giving them but it's actually very nutritionally similar to spruce seed, which is their primary food source in the Yukon. We study a lot of squirrels and so there's a lot of peanut butter to put out! It can also be a bit messy. In the winter we need to heat up the peanut butter next to our woodstove so that it can be poured into 1kg containers. Each of our supplemented squirrels gets one of these 1kg containers of peanut butter every two months through the winter. We have then been keeping track of their survival and reproduction to see how they differ between on food supplemented and control squirrels, which aren't receiving any food.
We will keep you updated on the results of the experiment as they come in.