Im so glad everyone is enjoying it
Im away from tomorrow so round 3 will be open until January 26th
(next week Wednesday). Seeing as you have a bit more time im going to try come up with some questions that make you think a little bit more
[January: Round 3]
In nature reptiles and other ectothermic animals have to regulate their body temperatures by making use of external energy sources and through physiological and behavioural regulatory responses. Why do you think that a Southern African Python would be found with its body submerged in the water early in the morning having been there the entire nigh?t, and secondly during what time of the year would you expect this to happen?Both of you gave me very similar answers here . You both described how they would use the water as an ambush site to capture potential prey which is right but I was looking for an answer more along the lines of why they would be found there for thermoregulatory reasons. The graph below is one I used in a project last year and will help to explain the answer a little better. So what you are looking at is a temperature profile of 2 pythons (one brooding and the other non-brooding) as well as their environment recorded over 20 days. The temperature data comes from ibuttons which have been in both pythons for quite a while, recording body temperature. 2 Other ibuttons were also used, one recording temperature above ground, and the other below ground (in shade and/or possibly water). For now ignore the brooding, non-brooding part. So now remember pythons are ectotherms and rely on environmental sources to regulate their body temperatures. during the day the maximum temperature of the hot probe (ibutton above ground, exposed) reaches levels well above the threshold tolerance of the pythons, so in that case once their body temperature (Tb) has reached a significantly high level during basking in the open (on rocks etc) they will move into shaded areas and often down burrows where the cold probe has been placed. Here their temperature will drop and they then will move out again in some circumstances to bask again thats why there are those spikes in the Tb. Now you can see that there i a huge variation in the temperatures recorded by the hot probe while those of the cold probe are much more stable. Also notice that during the night the temperature of the cold probe is higher than that of the hot probe. This is because from about 1m underground temperature remains fairly constant and in water the water looses heat to the environment at a much slower rate than terrestrial surfaces. So basically if the snake was to remain in water during the night its Tb would remain significantly higher than if it was not in water or similarly down a burrow. You would expect this situation to occur during winter months with lower night time temps. There have been records of pythons found dead exposed on the surface following a cold snap the night before because temperatures dropped too low. Thus it is sort of a behavioural form of thermoregulation.
Bonus for up to 5 points:
Following on with question 1. What are the differences in appearance and behaviour between a brooding and a non brooding python?It has been shown that brooding females have a much darker colour than females that do not have a clutch. This is believed to increase the efficiency of heat absorption during basking. This is important as the eggs must remain in a very narrow temperature range and this poses a challenge to the mother. In SA pythons do not undertake shivering thermogenesis (actively creating heat through micro-muscle contractions) like the closely related burmese python but instead must use behavioural thermoregulation to incubate their eggs. This means that their behaviour is very different to pythons without eggs. Firstly pythons and all snakes have a target body temperature towards which they aim. In pythons this is around 30-32 degrees. But when they are on eggs this changes dramatically and their target body temperature is now around 37-38 degrees. The python will thermoregulate to maintain their body temperatures as close to this target temperature as possible as this is the temperature at which they function most efficiently. The behaviour now changes and females with eggs will remain basking until they reach close to lethal temps and then return to incubate the eggs by wrapping around them (eggs are deposited in burrows). What i noticed as well is that females with eggs tend to have a body temperature that varies much less significantly than a female without eggs meaning a brooding female has a much narrower range of fluctuations in temperatures (lower standard deviation). Here is a table showing the target Tb's for a brooding and non brooding python.
Im sure you have all heard of corridors between natural areas being important for maintaining species persistence, but why is that? and then why is a reserve that is round in shape in terms of boundaries more likely to benefit species persistence (so that they do not go extinct) than a reserve that is square or oblong in shape? Firstly corridors are extremely important for species persistence because environments are extraordinarily complex and fragmentation reduces the efficiency of a number of environmental process. Animals cannot move between habitats, gene pools shrink and this loss in diversity makes it more likely for a species to go extinct. Its very interesting and I could spend a very long time explaining it .
The second part of the question basically utilises island biogeographic theory and applies it to conservation management. For those interested a book called song of the dodo by David Quamen is a MUST read . If you think about it small isolated fragments of habitat are virtually identical to islands, separated from the mainland or in this case a larger more diverse reserve. You also then have to think about perimeter or peninsula effects also known as edge effects which in its simplest form basically refers to how vulnerable the inhabitants of the reserve are to external influences, whether this be human induced or genetic. In terms of the genetic side of things a species is more vulnerable if there is a large perimeter as this influences the rates of immigration, emmigration as well as making it more likely that a population could become isolated, suffer from genetic bottlenecks and a whole host of other factors. So the diagram i quickly drew up explains things quite nicely in terms of optimal shape and arrangements of reserves or fragmented patches of habitat.
1: 1 large circle has less of a perimeter and thus less edge effects than several small patches (SLOSS:single large or several small argument)
2: circular shape less perimeter than an oblong shaped reserve
3: the first arrangements of fragments is ecologically more sound as there is an equal distance between each fragment while in the second the first and third are not equal.
4:Obviously it is better for patches to be closer together rather than further as this way ecological process and gene flow is more likely between the habitats that are closer.
5:And finally it is much better to have a corridor as explained earlier than no corridor.
Which will benefit from global warming more and why, trees (woody plant material) or grasses?(herbaceous plant material)
Trees and other woody plant material will benefit far more from increased levels of carbon dioxide. However in areas that receive greater amounts of rain, grasses will benefit as much if not more as they are able to utilise water more efficiently than trees. An increase in rainfall will result in an increase in the herbaceous plant material. I am only familiar with savannas so can only explain what will occur there, but there are many factors which need to be considered along with trees and grasses. herbivory, linked with fire frequency and nutrient cycling. Globally atmospheric concentrations of carbon dioxide are increasing and this I believe will result in bush encroachment (by woody plant material, trees and bushes) for a number of reasons. The first reason is that increased CO2 concentrations are expected to result in an increased supply of non-structural carbohydrates. These carbohydrates are essential to trees after they have sustained damage from fire or herbivory and allow the C3 plants to coppice (woody plants have a C3 photosynthetic pathway and therefore benefit from increased CO2 levels). Coppicing involves the re-growth of woody material and as such CO2 will improve the resprouting potential of trees. In savannas the height and therefore dominance of trees is controlled by fire especially when trees are within the flame zone. However, with improved resprouting potential more trees will be able to reach the fire escape zone more quickly and hence escape the fire and become more abundant resulting in bush encroachment. Other conditions which can result in bush encroachment would be where a section of savanna is free from fire and herbivory as here fire and herbivory cannot prevent the recruitment of trees. Fire is a very important factor in the maintenance of savannas and in the absence of fire trees can also increase in density and abundance resulting in bush encroachment as trees can now outcompete grasses. In areas where overgrazing occurs due to the overpopulation of herbivores as a result of the lack of predators; the relative absence of herbaceous plant material can result in bush encroachment due to lower levels of competition.
If you look at these pictures you will see that greater atmospheric levels of CO2 (Parts per million) will favour woody plant growth especially in savannas. Trees are able to grow faster, larger and due to increased availability of structural carbohydrates repair themselves more quickly (coppice). Their root systems become much thicker and more widespread, providing an increased surface area for water and nutrient absorption.
Why are termite mounds important in Savannas?Termite mounds are vital components of savanna ecosystems. In the kruger park they influence 19% of the total land surface area. That's a huge proportion of the land that is effected by these structures. Termites are basically ecosystem engineers as during the construction and habitation of their mounds they are responsible for bringing up minerals and nutrinets from deep below that would otherwise be unavailable to most vegetation on the surface. If you look at this image from kruger you can see all the white dots, those are termite mounds and the difference in colour is a good indication of the difference in soil type and characteristics.
Termites increase the concentration of essential nutrients in the soil creating vegetation that is more nutritious and palatable than surrounding vegetation and is often targeted by herbivores. They also aerate the soil and introduce course particles into otherwise fine sand resulting in soil into which water can infiltrate much more efficiently, thereby promoting plant growth. TM are used by aardvarks, other ecosystem engineers to create burrows which are vitally important to a whole range of species for shelter and reproduction. Now because the vegetation is more nutritious and therefore more palatable, TM will generally be more sparsely vegetated than surrounding areas that extend beyond the sphere of influence of the mound. In a savanna, an ecosystem in which fire is essential, the termite mounds act as refugia to small insects, mammals, reptiles etc as fires do not burn over the TM because there is very little vegetation to burn. Another important factor is that the termite mounds can then also play an important role as a seed bank from which vegetation can regrow.
You are lucky and you get to go on a guided walk in kruger. You happen to come across a river/stream and are forced to cross it. You stumble on a rock upending it and notice these little creatures stuck to the rock and swimming away from it. You immediately know they are stoneflies. Later on in the walk you cross another stream only this time you see tons of dragon fly nymphs ontop of the water.
From this what can you tell me about the difference in the water quality between the two rivers and about the rivers themselves (speed , depth )Water quality as well as stream characteristics can easily be identified by the macro-invertebrate assemblages that inhabit them as they are very specific in the conditions in which they can live due to their physiological and morphological characteristics.
Stoneflies will only occur in unpolluted rivers where there is an abundance of oxygen. They are sensitive to pollution as they have external gills, as well as brush like gills along the length of their bodies. This then tells you that this stream is fast flowing potentially with rapids (fast flowing water moving quickly over exposed rocks) and is relatively shallow in the part you crossed. The presence of rapids is an important part as with the water splashing into the air, the water becomes aerated to a much greater degree than a uniform flowing river. Fresh water ecologists use a sensitivity ranking for aquatic invertebrates. The scale ranges from 0-15 with 15 being insects which are very sensitive to water conditions (pollutants). Stoneflies have an average sensitivity of 13-14.
Odonata (dargon fly nymphs) however are more tolerant of pollution. They have three tiny gills on their abdomens and this makes them more tolerant of polluted water. They have an interesting form of locomotion where they suck water in through their gills and the squirt it out through their anus moving by jet propulsion! This means they will usually be found in streams that are deeper, slower moving and most likely a stagnant backwater section where they can breed.
Hope I have not gone overboard with the questions
ENJOY and ill "see" you all next week