Trends in wildlife rehabilitation rescues and animal fate across a six-year period in New South Wales, Australia

Abstract

Globally, millions of animals are rescued and rehabilitated by wildlife carers each year. Information gathered in this process is useful for uncovering threats to native wildlife, particularly those from anthropogenic causes. However, few studies using rehabilitation data include a diverse range of fauna, cover large geographical areas, and consider long-term trends. Furthermore, few studies have statistically modelled causes of why animals come into care, and what are their chances of survival. This study draws on 469,553 rescues reported over six years by wildlife rehabilitators for 688 species of bird, reptile, and mammal from New South Wales, Australia. For birds and mammals, 'abandoned/orphaned' and 'collisions with vehicles' were the dominant causes for rescue, however for reptiles this was 'unsuitable environment'. Overall rescue numbers were lowest in winter, and highest in spring, with six-times more 'abandoned/orphaned' individuals in spring than winter. Of the 364,461 rescues for which the fate of an animal was known, 92% fell within two categories: 'dead', 'died or euthanased' (54.8% of rescues with known fate) and animals that recovered and were subsequently released (37.1% of rescues with known fate). Modelling of the fate of animals indicated that the likelihood of animal survival (i.e. chance of: being released, left and observed, or permanent care), was related to the cause for rescue. In general, causes for rescue involving physical trauma (collisions, attacks, etc.) had a much lower likelihood of animals surviving than other causes such as 'unsuitable environment', 'abandoned/orphaned', and this also showed some dependence upon whether the animal was a bird, reptile, or mammal. This suggests rehabilitation efforts could be focused on particular threats or taxa to maximise success, depending on the desired outcomes. The results illustrate the sheer volume of work undertaken by rehabilitation volunteers and professionals toward both animal welfare and to the improvement of wildlife rehabilitation in the future.

Fig 1. Species accumulation curve for all animal species, showing the rate of new species records accumulating across survey years.

Survey year represents the year during the study period (i.e. 1 = 2013–14; 6 = 2018–19).

Fig 2. Cause for rescue (%) within each animal group, for top 10 highest ranked causes across all animals.

Fig 3. Number of rescue records per year for each animal group, and in total.

Fig 4. Cause for rescue by year for the 2013–14 to 2018–19 period, pooled for all animals and for top 10 highest ranked pooled causes.

Fig 5. Mean ± SE number of rescues per month pooled for all years, for each animal group and all animals combined.

Fig 6. Number of records per year over the survey period, for birds, reptiles, mammals, and all animals.

Fig 7. Mean number of rescues per month attributable to each of the top 8 pooled causes for rescue.

Fig 8. Percent (%) of rescues attributable to each of top 8 pooled causes for rescues within each month.

Fig 9. Percent (%) of rescues with a negative outcome for each group for each year, based on fate.

Fig 10. Likelihood of survival + 95% confidence intervals for birds and mammals when averaged, for each cause for rescue.

Fig 11. Likelihood of survival + 95% confidence intervals in relation to cause for rescue and animal group.

Fig 12. Response coefficients indicating the relative positive or negative response of bird and mammal subgroups amongst each other.

Fig 13. Likelihood of survival + 95% confidence intervals for reptiles in relation to cause for rescue.

Fig 14. Response coefficient (+ - 95% CI) of reptile subgroups indicating their relative positive or negative response amongst each other.