| 2024 | Leiden Conservation Foundation | 990PF | President | 1 | $0 | $0 | View return |
| 2023 | Leiden Conservation Foundation | 990PF | President | 1 | $0 | $0 | View return |
| 2022 | Leiden Conservation Foundation | 990PF | President | 1 | $0 | $0 | View return |
| 2021 | Leiden Conservation Foundation | 990PF | President | 1 | $0 | $0 | View return |
| 2021 | Cleveland Museum of Natural History | 990 | Honorary | 1 | $0 | $0 | View return |
| 2020 | Cleveland Zoological Society | 990 | Secretary | 4 | $0 | $0 | View return |
| 2020 | Leiden Conservation Foundation | 990PF | Director; President | 1 | $0 | $0 | View return |
| 2020 | Cleveland Museum of Natural History | 990 | Honorary | 1 | $0 | $0 | View return |
| 2019 | Leiden Conservation Foundation | 990PF | Director; President | 1 | $0 | $0 | View return |
| 2019 | Cleveland Zoological Society | 990 | Secretary | 4 | $0 | $0 | View return |
| 2019 | Cleveland Museum of Natural History | 990 | Honorary | 1 | $0 | $0 | View return |
| 2019 | Giraffe Conservation Foundation USA | 990 | Director | 5 | $0 | $0 | View return |
| 2018 | Leiden Conservation Foundation | 990PF | Director; President | 1 | $0 | $0 | View return |
| 2018 | Cleveland Zoological Society | 990 | Secretary | 4 | $0 | $0 | View return |
| 2018 | Giraffe Conservation Foundation USA | 990 | President | - | $0 | $0 | View return |
| 2018 | Cleveland Museum of Natural History | 990 | Honorary | 1 | $0 | $0 | View return |
| 2017 | Leiden Conservation Foundation | 990PF | Director; President | 1 | $0 | $0 | View return |
| 2017 | Giraffe Conservation Foundation USA | 990 | President | - | $0 | $0 | View return |
| 2017 | Cleveland Museum of Natural History | 990 | Honorary | 1 | $0 | $0 | View return |
| 2016 | Leiden Conservation Foundation | 990PF | Director; President | 1 | $0 | $0 | View return |
| 2016 | Giraffe Conservation Foundation USA | 990 | President | 0.5 | $0 | $0 | View return |
| 2016 | Cleveland Museum of Natural History | 990 | Honorary | 1 | $0 | $0 | View return |
| 2015 | Leiden Conservation Foundation | 990PF | Director; President | 1 | $0 | $0 | View return |
| 2015 | Cleveland Museum of Natural History | 990 | Honorary | 1 | $0 | $0 | View return |
| 2014 | Leiden Conservation Foundation | 990PF | Director; President | 1 | $0 | $0 | View return |
| 2014 | International Penguin & Marine Mammal Foundation Inc | 990EZ | Outgoing Chairman | 1 | $0 | $0 | View return |
| 2014 | Cleveland Museum of Natural History | 990 | Honorary | 1 | $0 | $0 | View return |
| 2013 | Leiden Conservation Foundation | 990PF | Director; President | 1 | $0 | $0 | View return |
| 2013 | International Penguin & Marine Mammal Foundation Inc | 990EZ | Chairman, Director | 1 | $0 | $0 | View return |
| 2013 | Cleveland Museum of Natural History | 990 | Standing Trustee | 1 | $0 | $0 | View return |
| 2012 | Leiden Conservation Foundation | 990PF | Director; President | 1 | $0 | $0 | View return |