January 25, 2010 – PZP’s Effects, part 2: Behavior

Wild horses have very well-defined social characteristics. It is thus important that management not cause significant changes in their behavior. PZP’s effect on the behavior of wild horses has been the subject of much speculation, debate, and controversy. However, discussions of such effects should be in the context of findings from well-designed scientific studies. The results of such studies have been performed, and these will be the topic of today’s discussion.

We are asking what seems to be a straightforward question: Do wild horses treated with PZP behave different than untreated wild horses? In reality, this is a pretty complex question to try to answer. To start with, a large sample of treated and untreated individuals must be defined so that thorough observations are made. Also, there must be a set of defined behaviors that can be observed and measured. Numerous observations must then be made over a significant length of time so that a wide range of data is collected. This data must then be analyzed so that any statistically significant differences in the behavior of treated and untreated mares can be detected. This is all made more complex by the fact that wild horses are so socially complex. Despite these challenges, there have been studies done to try and answer the above question.

January 21, 2010 – The Mustang Project

A fairly new blog has been taking off quickly, and I have really enjoyed watching it grow. The Mustang Project (http://themustangproject.wordpress.com/) is an excellent source for factual source material on a lot of the proposals, projects, topics, and the like that are often at the center of controversy. This blog project is a very worthwhile one to follow, and I highly recommend visiting it for information to become better informed on relevant issues.

January 21, 2010 – PZP’s Effects, part 1: Injection Site Reactions & Reproductive Organs

Research on PZP has not only focused on desired effects; it has also focused on undesired side-effects. These effects have been the subject of numerous studies that date from the early 1990’s until fairly recently. Today we will be focusing on two different physiologic effects that are relevant to studies on the use of PZP in wild horses: injection site reactions and effects on the reproductive organs.

Injection Site Reactions

Injection site reactions are often generalized as being abscesses. However, there are a number of different reactions. A recent study (Roelle, J.E. and Ransom J.I., 2009) defined four types of possible reactions:

• Abscesses: Open sores, possible with drainage, at the injection site.
• Nodules: Circular, raised areas at the injection site.
• Swelling: A raised area, that is not as defined as a nodule, at the injection site.
• Stiffness: A case where the natural movement of the leg associated with the injection site has been affected.

January 19, 2010 – PZP’s Efficacy & Population Effect

In past posts, I have presented information on the technical aspects of PZP. From this, it can be seen why PZP should be able to work in the management of wild horse populations. It can also be seen that it is feasible to use it on wild horses. Now, though, we need to think about how it actually works on wild horses. Today I will be discussing an important requirement for PZP, and any wildlife contraceptive, which is efficacy. That is, what percentage of a treated group of mares will experience a reduction in foaling due to PZP? Also, I will be discussing the demographics of populations managed through fertility control. The data for today’s topics mainly originated from Assateague Island. This is because that population has been managed exclusively with PZP for many years, and it is also a very well-studied herd.