Use local knowledge to find out about behavior that may make it easier to capture or recapture the organism. Avoid the scientific hubris that you know all about the species.

make sure the mark recapture is necessary or if mapped observations would suffice.

Use local knowledge to find out about behavior that may make it easier to capture or recapture the organism. Avoid the scientific hubris that you know all about the species.

make sure the mark recapture is necessary or if mapped observations would suffice.

3 things immediately spring to mind:

1) Make sure markings cannot be confused with any natural phenomenon. In a crab mark-recapture effort I worked on, we clipped specific carapace teeth (spines on the body) to mark them. However, crabs molt (which can regrow the teeth) and they can loose them naturally, so there were many times we had long debates trying to decide if it was clipped or not.

2) Mark lots of specimens. In a 100,000 individual population, ten marked will not be enough. 

3) Consider timing and location of release. A colleague once told me of a mark-recapture effort with a small crab, Hemigrapsus oregonensis, where they had marked hundreds of crabs and released them, just to have seagulls descend and eat most of their marked crabs. I can easily imagine other situations where you might release marked organisms into a bad situation.

I hope this is helpful. Best of luck with your presentation.

Hi. Two important things:

1. Be sure no loss or misidentification of marks. Maybe could be useful use of double marks.

2. The marked individuals would be a representative sample of the study population.

Regards,

Jose

I will add a few things I have been thinking of: 1) choose a plot size that is big enough to contain enough animals that you will likely capture a decent number, but small enough that you can sample it adequately with the people/time/traps you have available. 2) try to be as consistent as possible in sampling effort between plots and across time. 3) be aware that detection probability can be vastly different between observers, between habitat types, or between sampling periods. This can be dealt with to a degree with the analysis, but if the variance can be reduced at the outset it is better.

I'd recommend starting from your planned analysis/ what you want to know and working backwards to determine what the mark-recapture study design should be. Some questions to consider before initiating a project: Is your population open or closed? That will have a lot do with how you set up your sampling periods. Will you need several successive nights/days in the field or, if not, how much can you get done in one day? It's also important to consider the other variables you want to measure: temp, humidity, animal size class. If you will be sampling over several years it may be important to go at the same time every year. Are your animals trap shy or happy?  

From my own experience it is the analysis part of the project that is the hardest.I would suggest doing a lot of reading of other studies that have used the same software for the same kind of analysis. Collecting the data is the fun part!

 Also, regarding marking- it may not be possible or a good idea to mark all size classes. If you get juveniles they may be more susceptible to disease or depredation depending on the marks used. We had a case where we were gluing number tags on snails and later a paper came out that said the specific type of glue attracted rats- a snail predator! We no longer use the glue. Anyway, if you are not marking all size classes that is something to consider.

Jenny, number tags on snails sounds kind of adorable! We used silicon glue to attach transmitters to horned lizards. I don't think it was an attractant, per se, but kit foxes probably noticed the smell and investigated. Predation levels dropped off after the first week of having a transmitter, which could have been due to the glue smelling less over time (but could also have been due to the lizard behaving more normally after habituation). 

Kevin, that is an interesting point. It's important to understand tagging/marking effects and how they may influence post release survival. Also, it is important to understand species specific rates of tag retention/loss (e.g. salmon smolts will often expel surgically implanted acoustic transmitters while other species will have high rates of retention).

I am not sure someone has not implied this above. But the behavior of the individual organisms is likely to make them easier to capture. For instance if you were collecting almost any species of caterpillar you would tend to collect a disproportionate number of parasitized individuals. Maybe you can somehow include this in your experimental design.  (I seem to recall that there is a report somewhere that this principle even applies to seals).

Kevin, We use photo ID software now instead of the little glued numbers. When I first learned CMR we were using pens with nibs and india ink and giving them a light coat of some kind of shellac (clear nail polish?). Anyway the Photo ID brings it's own level of complexity to things. If you have time and wouldn't mind sending a copy, I'd like to see your presentation when it's done.