Vertebrate Pests: The Rodent Explosion Part II

This article is a continuation of the November 2000 column titled Are We Having A Rodent Explosion? (Part 1). In Part 2, we continue to examine the various issues and factors that affect increases and decreases in urban rodent populations. Also, there is a correction to the November column: A misspelling resulted in the spell checker substituting the word "restraint" for restaurant.

Humans vs. rodents. Is there currently an explosion of rodents? I’m not so sure. I believe it’s more like rodent populations have remained on a slow boil for perhaps two centuries or more. Certainly, some relatively recent societal and environmental factors have benefited rodent populations more than in years past, resulting in local and temporal "explosions." But we also have to ask ourselves, "How effective and efficient are we (as a competing mammal species) in eliminating rats and mice in our environments?" Are we really serious about eliminating rats and mice? We say we are. But if we take a step back and consider this question, it sure doesn’t look like it.

Proactive vs. reactive. Humans certainly are not proactive in eliminating rodents from urban ecosystems. In fact, with almost all pests, we tend to be reactive. Most people do not spend time in the course of a week (or a month) inspecting whether or not a mouse, rat, cockroach or other pest has moved into their home or work space. Moreover, few people proactively inspect their urban spaces to eliminate any conditions that are conducive to attracting and allowing rodents to exist or proliferate nearby. "Pest preventive activities" simply do not occur to the average person on a regular basis.

A more serious attitude on our part would involve a coordinated effort of everyone paying attention to their own clutter and organizing their own work-spaces and homes. Overall, humans are not this well organized. Consider that even relatively small areas, or a few urbanites, (e.g., 10 dirty apartments out of 100), allow local rodent populations to persist and proliferate despite control programs. People react to rodents only after enough rodents are seen scurrying about or they are discovered attacking foods or gnawing on wires. By this time, the rodents have become numerous and more widely distributed, rendering rodent elimination programs more unlikely due to the expense.

Harvesting vs. Eliminating. Perhaps, more often than we would like to admit, humans merely harvest rodent populations. Upon discovering rodents around the house or workplace, many people respond by putting out an over-the-counter bait or setting a trap or two. Except for minor simple infestations, such efforts usually result in only partial control. In other words, these efforts are merely a "harvesting off" of some of the rodents within a larger population.

Then, when "do-it-yourselfers" realize they need a professional, often their choice is price driven and they select the lower bid, hoping for an inexpensive and quick elimination. Unfortunately, most people do not realize that the elimination of local rodent populations requires thorough efforts on the part of the pest professional. It takes time to inspect and service hard-to-reach areas such as suspended ceilings and utility chases. Additional costs are incurred because the clients themselves must take an active role in eliminating conducive conditions. Such programs (i.e., IPM) require time on everyone’s part and thus cost more.

Moreover, different companies, groups and various untrained do-it-yourselfers may all be doing rodent control programs conducted around just one city block. Some programs may be thorough, others not so much. Consequently, people are not consistent in implementing quality control programs on the broad scale. Rodents from poorly implemented programs constantly replace those that were killed in well-implemented programs in nearby areas. As a result of control programs not being priced according to the actual effort needed to eliminate rodents, we harvest instead of eliminate.

Refuse Management. Norway rat populations require a fair amount of food to sustain healthy and expanding populations. As such, areas experiencing rat "explosions" are sometimes associated with inefficient or improper refuse management operations.

Some urbanites, attempting to avoid spending money on their refuse, simply "dump" their refuse in plastic bags outside of their homes and stores, allowing rodents easy access to food trash. Obviously, refuse programs must be carefully analyzed to ensure the availability of food trash to the local rats is minimized. This involves the frequency of trash pick up, as well as the specific details of the entire program such as the specific containers and the construction, materials and design of the containers. All of these factors can affect rat accessibility of the trash once it is inside the container.

"Control-Shy" Rodents? The public, as well as some pest management professionals, have been speculating over the past few years that perhaps the increase in rodents is a result of rodents becoming "more difficult" to kill. In other words, maybe our tools are no longer as effective as in years past. Some speculate that the rodents are becoming trap shy, bait shy or are becoming physiologically resistant to current rodenticides. Anyone experienced in rodent control can attest to the occasional failure of any particular tool against a specific rodent population. Such failures have been periodically occurring for years. Whether or not these occurrences are increasing would make for a fascinating scientific study, although difficult to do on any scale that would make for a meaningful " big picture" inference.

The War on Rats. Recently, New York City held a "rat summit," vowing to declare war on rats. Mayor Rudolf Giuliani commented that NYC "kills more rats than anybody else." New York City’s long-time rat expert Randy Dupree stated during the summit that, "What we need is for everyone to join in on the war against rats." His comment pretty much sums it up. Pest management professionals do not have magic wands to eliminate rats and mice in urban areas where perhaps trash is providing essential resources that enable rodents to rebound from extermination programs. The public must work together with rodent control personnel.

Such earnest programs as the New York City summit and effort are commendable. But it won’t be easy. When it comes to pest elimination programs, the saying, "Those who don’t learn from the past are doomed to repeat it" is applicable. Consider a letter written in 1841 from the then New York City Mayor Robert H. Morris to the famous naturalist and artist John James Audubon. In an accommodating effort to provide the artist with specimens while also help to eliminate some of the NYC rats, the mayor wrote: "Permission is hereby granted to Mr. Audubon to shoot rats at the Battery early in the morning so as not to expose the inhabitants in the vicinity to danger."

I wonder if the Brooklyn Battery residents 150 years ago felt they needed help with their current rat explosion?