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We investigated factors affecting the success of 14 species of ungulates introduced to New Zealand around 1851-1926. The 11 successful species had a shorter maximum life span and were introduced in greater numbers than the three unsuccessful species. Because introduction effort was confounded with other life-history traits, we examined whether independent introductions of the same species were more likely to succeed when a greater number of individuals were introduced. For the six species with introductions that both succeeded and failed, successful introductions always involved an equal or greater number of individuals than unsuccessful introductions of the same species. For all independent introductions, there was a highly significant relationship between the number of individuals introduced and introduction success. When data for ungulate and bird introductions to New Zealand were combined, a variable categorizing species as ungulate or bird was a highly significant predictor of introduction success, after variation in introduction effort was controlled. For a given number of individuals introduced, ungulates were much more likely to succeed than birds. size," has a strong theoretical basis for determining introduction success. Demographic stochasticity, the result of random and independent births and deaths, can lead to population extinction, the probability of which is inversely proportional to population size ( In this article, we compare the factors affecting the introduction success of ungulate and bird species introduced to New Zealand. The objectives of our study were twofold: first, to identify which life-history and/or ecological variables predict the success of 14 ungulate species introduced to New Zealand and to determine whether introduction effort was a factor influencing introduction success and, second, to determine whether species of ungulates and birds differed in their probability of success when introduced to New Zealand. Keywords Methods Data SourcesWe searched the literature for information on the introduction of ungulates into North, South, and Stewart Islands ("New Zealand"). Our primary sources were Thomson ( Introductions were defined as "successful" if the species had wild populations in New Zealand in 1996 or previously had a self-sustaining wild population that was eradicated by hunting. Only one species, Axis axis, met the latter criterion. Introductions not meeting these criteria were termed "unsuccessful." There is uncertainty as to whether moose (Alces alces) were extant in New Zealand in 1996 (Davidson and Tustin 1990), but based on the evidence in Tustin (1998), we concluded that a population was present.To determine whether introductions failed because species were introduced into areas that lacked suitable habitat, we quantified the propensity of each species to utilize 10 major habitat types in New Zealand (table 1). Each habitat was scored as 1 for "suitable" and 0 for "unsuitable" based on descriptions of each species' habitat use outside New Zealand (see table...

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