Estimating the annual distribution of monarch butterflies in Canada over 16 years using citizen science data

Monarch butterflies (Danaus plexippus, Linnaeus, 1758) are comprised of two migratory populations separated by the Rocky Mountains and are renowned for their long-distance movements among the United States, Canada, and Mexico. Both populations have declined over several decades across North America prompting all three countries to evaluate conservation efforts. Monitoring monarch distribution and abundance is a necessary aspect of ongoing management in Canada where they are a species at risk. We used presence-only data from two citizen science data sets to estimate the annual breeding distribution of monarch butterflies in Canada between 2000 and 2015. Monarch breeding distribution in Canada varied widely among years owing to natural variation, and when considering the upper 95% of the probability of occurrence, the annual mean breeding distribution in Canada was 484 943 km(2) (min: 173 449 km(2); max: 1 425 835 km(2)). The area of occurrence was approximately an order of magnitude larger in eastern Canada than in western Canada. Habitat restoration for monarch butterflies in Canada should prioritize productive habitats in southern Ontario where monarchs occur annually and, therefore, likely contribute most to the long-term viability of monarchs in eastern North America. Overall, our assessment sets the geographic context to develop successful management strategies for monarchs in Canada.Liber Ero Postdoctoral Fellowship; University Research Chair from the University of GuelphOpen access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

An Evaluation of Studies on the Potential Threats Contributing to the Decline of Eastern Migratory North American Monarch Butterflies (Danaus plexippus)

The migratory monarch butterflies (Danaus plexippus) of eastern North America have undergone large-scale declines, which may be attributable to a variety of underlying causes. The uncertainty about the primary cause of declines and whether individual threats are likely to increase in the future presents challenges for developing effective conservation management and policy initiatives that aim to improve population viability. This paper identifies five potential threats and classifies these threats according to the types of studies (observational, experimental, simulation/models) and their current impact and anticipated risk. Broadly, the threats can be classified into five categories: (1) change in suitable abiotic environmental conditions; (2) deforestation in the overwintering range; (3) exposure to contaminants including the bacteria Bacillus thuringiensis, herbicides, and insecticides; (4) loss of breeding habitat; and (5) predation, parasitism, and species-specific pathogens. The vast distribution of the monarch butterfly makes it likely that population declines are attributed to a suite of interacting factors that vary spatially and temporally in their contribution. Nonetheless, the published papers we reviewed suggest the decline in suitable environmental conditions in addition to overwintering (i.e., deforestation) and breeding habitat loss are the most likely threats to continue to affect the population viability of monarch butterflies

Correction: Multistate matrix population model to assess the contributions and impacts on population abundance of domestic cats in urban areas including owned cats, unowned cats, and cats in shelters.

[This corrects the article DOI: 10.1371/journal.pone.0192139.]

Multistate matrix population model to assess the contributions and impacts on population abundance of domestic cats in urban areas including owned cats, unowned cats, and cats in shelters

<div><p>Concerns over cat homelessness, over-taxed animal shelters, public health risks, and environmental impacts has raised attention on urban-cat populations. To truly understand cat population dynamics, the collective population of owned cats, unowned cats, and cats in the shelter system must be considered simultaneously because each subpopulation contributes differently to the overall population of cats in a community (e.g., differences in neuter rates, differences in impacts on wildlife) and cats move among categories through human interventions (e.g., adoption, abandonment). To assess this complex socio-ecological system, we developed a multistate matrix model of cats in urban areas that include owned cats, unowned cats (free-roaming and feral), and cats that move through the shelter system. Our model requires three inputs—location, number of human dwellings, and urban area—to provide testable predictions of cat abundance for any city in North America. Model-predicted population size of unowned cats in seven Canadian cities were not significantly different than published estimates (p = 0.23). Model-predicted proportions of sterile feral cats did not match observed sterile cat proportions for six USA cities (p = 0.001). Using a case study from Guelph, Ontario, Canada, we compared model-predicted to empirical estimates of cat abundance in each subpopulation and used perturbation analysis to calculate relative sensitivity of vital rates to cat abundance to demonstrate how management or mismanagement in one portion of the population could have repercussions across all portions of the network. Our study provides a general framework to consider cat population abundance in urban areas and, with refinement that includes city-specific parameter estimates and modeling, could provide a better understanding of population dynamics of cats in our communities.</p></div

Experimental examination of intraspecific density-dependent competition during the breeding period in monarch butterflies (Danaus plexippus)

A central goal of population ecology is to identify the factors that regulate population growth. Monarch butterflies (Danaus plexippus) in eastern North America re-colonize the breeding range over several generations that result in population densities that vary across space and time during the breeding season. We used laboratory experiments to measure the strength of density-dependent intraspecific competition on egg laying rate and larval survival and then applied our results to density estimates of wild monarch populations to model the strength of density dependence during the breeding season. Egg laying rates did not change with density but larvae at high densities were smaller, had lower survival, and weighed less as adults compared to lower densities. Using mean larval densities from field surveys resulted in conservative estimates of density-dependent population reduction that varied between breeding regions and different phases of the breeding season. Our results suggest the highest levels of population reduction due to density-dependent intraspecific competition occur early in the breeding season in the southern portion of the breeding range. However, we also found that the strength of density dependence could be almost five times higher depending on how many life-stages were used as part of field estimates. Our study is the first to link experimental results of a density-dependent reduction in vital rates to observed monarch densities in the wild and show that the effects of density dependent competition in monarchs varies across space and time, providing valuable information for developing robust, year-round population models in this migratory organism

Proportion of free-roaming cats adopted off the street.

<p>The annual proportion of free-roaming cats adopted off the street (black line, right axis) was a product of two relationships: the proportion of cat owners that will seek to adopt a free-roaming cat and the proportion of free-roaming cats that are available to be adopted. The proportion of cat owners that will seek to adopt a free-roaming cat exponentially decreases as where <b><i>a</i></b> = <b>1.20397</b>, <b><i>N</i>_<i>o</i></b> is the number of owned cats and <b><i>K</i>_<i>o</i></b> owned cat carrying capacity increases (blue line, left axis). The proportion of free-roaming cats that are available to be adopted (i.e. given temperament, personality and need for resources) is a logistic relationship of the form where <b><i>a</i></b> = <b>3.87637</b>, <b><i>b</i></b> = −<b>5</b>, <b><i>N</i>_<i>f</i></b> is the number of free-roaming cats, and <b><i>K</i>_<i>f</i></b> is free-roaming cats carrying capacity (yellow line, left axis). The dotted line is the value from New et al. [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0192139#pone.0192139.ref068" target="_blank">68</a>] that found 0.243 of owned cats were acquired as strays and was used as a guide point to build the logistic function and assumes the system studied by New et al. [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0192139#pone.0192139.ref068" target="_blank">68</a>] was at equilibrium (black dot).</p

Demographic vital rates used in a multistate matrix population model of domestic cats with an annual time step.

<p>Presented are survival (<i>s</i>), sterilization rate (<i>n</i>), and fecundity (<i>f</i>) for owned cats, free-roaming cats, feral cats, and cats moving between these states via the shelter system. Survival and sterilization are annual probabilities whereas fecundity is the number of female kittens produced per female per year. Some vital rates are density dependent. Listed are the state and stage of the cat, the variable in the population model, the value or equation for the vital rate, and references that inform parameterization. Note that values may differ slightly from those presented in the original source and that if left blank the variable was assumed for this model. The number of litters per female per year was where 149 is the number of days required to produce 1 litter (pregnancy lasts 65 days, weaning young requires 84 days) and <i>b</i> is the length of the breeding season in days.</p

A schematic diagram of the population model for cats.

<p>(A) Biological life-cycle diagram for domestic cats. Stage 1 are intact juvenile cats, stage 2 are intact adult cats, stage 3 are sterilized juvenile cats, and stage 4 are sterilized adult cats. Parameters shown include survival (<i>s</i>), fecundity (<i>f</i>), and sterilization <i>(n</i>); the values are presented in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0192139#pone.0192139.t001" target="_blank">Table 1</a>. Solid circles indicate intact life stages (reproductive) while dashed circles indicate sterilized life stages (non-reproductive) age categories. The time of sterilization within the life cycle is indicated with dashed lines. Subscripts on vital rates refer to kittens (0) and adults (1). (B) State and transition of domestic cats. Models for cities in North America considered in this paper used a four-state model that classified unowned cats as either free-roaming or feral cats. Note that the same biological life-cycle graph in (A) is found in each state in the model but will have different values for demographic vital rates.</p